#include <algorithm>
#include <bitset>
#include <tuple>
#include <cstdint>
#include <cstdio>
#include <cctype>
#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <limits>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using ll = long long; 
using ld = long double;
#define endl "\n"
//#define int long long
#define ALL(x) begin(x),end(x)
#define RALL(a) (a).rbegin(), (a).rend()
#define _CRT_SECURE_NO_WARNINGS
#define rep(i, n) for (int i = 0; i < n; i++)
const int MOD = 1e9 + 7;
const ll INF = 1LL << 60;
const int inf = 1 << 25;
constexpr long double pi = 3.141592653589793238462643383279;
int dx[] = { 1,0,-1,0 };
int dy[] = { 0,1,0,-1 };
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
ll fact(ll i) {
    if (i == 0) return 1;
    return ((fact(i - 1)) * i) % MOD;
}
ll gcd(ll a, ll b) {
    if (b == 0) return a;
    return gcd(b, a % b);
}
ll lcm(ll a, ll b) {
    return a * b / gcd(a, b);
}
ll keta(ll n) {
    if (n == 0) return 1;
    ll count = 0;
    while (n != 0) {
        n /= 10;
        count++;
    }
    return count;
}
ll ketasum(ll n) {
    ll sum = 0;
    while (n != 0) {
        sum += n % 10;
        n /= 10;
    }
    return sum;
}
ll mch(ll n) {
    if (n == 1) return 1;
    else return n * mch(n - 1);
}
ll modpow(ll a, ll n, ll mod) {
    ll hi = 1;
    while (n > 0) {
        if (n & 1) hi = hi * a % mod;
        a = a * a % mod;
        n >>= 1;
    }
    return hi;
}
bool is_prime(const unsigned n) {
    switch (n) {
    case 0: // fall-through
    case 1: return false;
    case 2: // fall-through
    case 3: return true;
    } // n > 3 が保証された
    if (n % 2 == 0 || n % 3 == 0) return false;
    for (unsigned i = 5; i * i <= n; i += 6) {
        if (n % i == 0) return false; // (6の倍数)-1
        if (n % (i + 2) == 0) return false; // (6の倍数)+1
    }
    return true;
}
/*signed*/int main(void) {
    int n, m; 
    cin >> n >> m;
    vector<pair<int, int>> p(m);
    rep(i, m) {
        int s, c; 
        cin >> s >> c;
        s--;
        p[i] = make_pair(s, c);
    }
    rep(i, 1000) {
        string s = to_string(i);
        if (s.size() == n) {
            bool ans = true;
            rep(j, m) {
                if ((s[p[j].first] - '0') != p[j].second)ans = false;
            }
            if (ans) {
                cout << i << endl;
                return 0;
            }
        }
    }
    cout << -1 << endl;
    return 0;
}
#include <bits/stdc++.h>
using namespace std;
#define mod 1000000007
#define ll long long int
#define pb push_back
typedef pair<ll,ll> ipair;
#define F first
#define S second
 
/*
//functions from gfg
 
long long int power(long long int x,long long int y,long long  int p)
{
    long long int res = 1;     // Initialize result
 
    x = x % p;  // Update x if it is more than or 
                // equal to p
 
    while (y > 0)
    {
        // If y is odd, multiply x with result
        if (y & 1)
            {//d=(long double)x/p;
            res = (res*x) % p;
            }
 
        // y must be even now
        y = y>>1; // y = y/2
        x=(x*x)%p;
        
    }
    return res%p;
}
 
long long int gcd(long long int a,long long int b) 
{ 
    if (a == 0) 
        return b; 
    return gcd(b % a, a); 
}
 
long long int binomialCoeff(long long int n, ll k) 
{ 
    ll res = 1; 
  
    // Since C(n, k) = C(n, n-k) 
    if (k > n - k) 
        k = n - k; 
  
    // Calculate value of [n*(n-1)*---*(n-k+1)] / [k*(k-1)*---*1] 
    for (ll i = 0; i < k; ++i) 
    { 
        res *= (n - i); 
        res /= (i + 1); 
    } 
  
    return res; 
} 
 

void sieve(int n, vector<ll> &primes) 
{ 
    vector<int> prime(n,1);
    ll p;
    for ( p=2; p*p<=n; p++) 
    { 
        // If prime[p] is not changed, then it is a prime 
        if (prime[p] == 1) 
        { 
            
            for (int i=p*p; i<=n; i += p) 
                prime[i] = 0; 
        } 
    } 
  
    for(p=2;p<=n;p++)
    {
        if(prime[p])
        primes.pb(p);
    }
   
} 


void dfs(vector<ll> adj[] ,ll src,vector<ll> &vis)
{
    vis[src]=1;
    for(ll i=0;i<adj[src].size();i++)
    {
        if(vis[adj[src][i]]==0)
        dfs(adj,adj[src][i],vis)
    }
}
 
*/

int main() {
    ios_base::sync_with_stdio(false);
    std::cin.tie(NULL);
    std::cout.tie(NULL);
    
    
    ll n,i,j,p,k,m,t,ans=0;
    cin>>n>>t;
    ll dp[3005][3005];
    memset(dp, 0, sizeof(dp)); 
    vector<ll> a(n),b(n);
    vector<pair<ll,ll> > val(n);
    for(i=0;i<n;i++)
    {
        cin>>a[i]>>b[i];
        val[i].F=a[i];
        val[i].S=b[i];
    }
    sort(val.begin(),val.end());
    for(i=0;i<n;i++)
    {
        a[i]=val[i].F;
        b[i]=val[i].S;
    }
    for(i=0;i<t;i++)
    {
        for(j=0;j<n;j++)
        {
            if(i+a[j]<t)
            {
                dp[j+1][i+a[j]] = max(dp[j][i]+b[j],dp[j+1][i+a[j]]);
            }
            
            dp[j+1][i] = max(dp[j][i],dp[j+1][i]);
            
        }
    }
    for(i=0;i<n;i++)
    {
        ans=max(ans,dp[i][t-1]+b[i]);
    }
    cout<<ans<<endl;
    
    // for(i=0;i<n;i++)
    // {
    //     cout<<a[i]<<" ";
    // }
    // cout<<endl;
    
    return 0;
}