#include <bits/stdc++.h>
using namespace std;

const long long mod = 1e9 + 7;

using ll = long long;
using pii  = pair<int, int>;
using pll = pair<ll, ll>;
#define ull unsigned long long
#define ld long double
#define vi vector<int>
#define vll vector<ll>
#define vc vector<char>
#define vs vector<string>
#define vpii vector<pii>
#define vpll vector<pll>

#define rep(i, n) for (int i = 0, i##_len = (n); i < i##_len; i++)
#define rep1(i, n) for (int i = 1, i##_len = (n); i <= i##_len; i++)
#define repr(i, n) for (int i = ((int)(n)-1); i >= 0; i--)
#define rep1r(i, n) for (int i = ((int)(n)); i >= 1; i--)

#define sz(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()

#define SORT(v, n) sort(v, v + n);
#define VSORT(v) sort(v.begin(), v.end());
#define RSORT(x) sort(rall(x));
#define pb push_back
#define mp make_pair

#define INF (1e9)
#define PI (acos(-1))
#define EPS (1e-7)

ull gcd(ull a, ull b) { return b ? gcd(b, a % b) : a; }
ull lcm(ull a, ull b) { return a / gcd(a, b) * b; }

int main(){
    int n, m;
    cin >> n >> m;
    vi s(m), c(m);
    rep(i, m) {
        cin >> s[i] >> c[i];
        s[i]--;
    }
    vi q(n, -1);
    rep(i, m) {
        if (q[s[i]]!=-1 && q[s[i]]!=c[i]) {
            cout << -1 << endl;
            return 0;
        }
        else q[s[i]] = c[i];
    }
    if (n>1 && q[0]==0) {
        cout << -1 << endl;
        return 0;
    }
    int b = 1, e = 10;
    rep(i, n-1) {
        b *= 10; e *= 10;
    }
    if (n == 1) b = 0;
    for (int i=b; i<e; ++i) {
        int i2 = i;
        bool ok = true;
        repr(j, n) {
            if (q[j]!=-1 && i2%10!=q[j]) ok = false;
            i2 /= 10;
        }
        if (ok) {
            cout << i << endl;
            return 0;
        }
    }
    cout << -1 << endl;
    return 0;
}

// lcmとかはg++ -std=c++17 default.cppみたいなかんじで
#include <bits/stdc++.h>
#define mod 1000000007
#define INF 1001001001
#define ll long long
#define ln cout<<endl
#define Yes cout<<"Yes"<<endl
#define No cout<<"No"<<endl
//#define double long double
#define REP(i,m,n) for(ll i=(ll)(m);i<(ll)(n);i++)
#define rep(i,n) REP(i,0,n)
#define rep1(i,n) REP(i,1,n+1)
using namespace std;

int main() {
    cin.tie(0);
   	ios::sync_with_stdio(false);

    ll a,b,c,n,maxi=0,f=0,mini=INF;
    ll sum=0;
    string str,sub;
    ll h,w;
    ll m;
    cin>>n>>m;
    if(m==0){
        if(n==1){
            cout<<0<<endl;
        }else if(n==2){
            cout<<10<<endl;
        }else{
            cout<<100<<endl;
        }
        return 0;
    }
    vector<pair<ll,ll>> s(m);

    rep(i,m){
        cin>>a>>b;
        s[i]=make_pair(a,b);
    }
    f=0;
    sort(s.begin(),s.end());
    sum=0;
            if(s[0].first==1) {
                //sum-=100;
                if(s[0].second==0&&n!=1) f=1;

                sum+=100*s[0].second;
            }
            if(s[0].first==2){
                //if(s[0].second==0&&n==2) f=1;

                sum+=10*s[0].second;
               // sum-=10;
            } 
            if(s[0].first==3){
                //sum-=1;
                sum+=1*s[0].second;
            } 
    for(ll i=1;i<m;i++){
        if(s[i-1].first==s[i].first&&s[i-1].second!=s[i].second) f=1;
        else if(s[i-1].first==s[i].first&&s[i-1].second==s[i].second) continue;
        else{
            if(s[i].first==1) {
               // sum-=100;
               if(s[i].second==0&&n!=1) f=1;
                sum+=100*s[i].second;
            }
            if(s[i].first==2) {
               // sum-=10;
                sum+=10*s[i].second;
            }
            if(s[i].first==3) {
              //  sum--;
                sum+=1*s[i].second;
            }
        }
    }
    if(n==1&&sum!=0) sum/=100;
    if(n==2&&sum!=0) sum/=10;
    if(n==3&&sum!=0&&sum<100) sum+=100;
    if(n==2&&sum<10) sum+=10;
    if(f!=1&&sum==0&&n==1){
        cout<<0<<endl;
        return 0;
    }
    
    if(f==1){
        cout<<"-1"<<endl;
    }else{
        cout<<sum<<endl;
    }
    return 0;
}
