#include <bits/stdc++.h>
#include <ext/rope>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define int long long
#define pb push_back
#define x first
#define y second
#define mk(a,b) make_pair(a,b)
#define rr return 0
#define sqr(a) ((a)*(a))
#define all(a) (a).begin(), (a).end()
#define sz(a) (int)(a).size()

using namespace std;
using namespace __gnu_cxx;
using namespace __gnu_pbds;

using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

template<class value, class cmp = less<value> >
using ordered_set = tree<value, null_type, cmp, rb_tree_tag, tree_order_statistics_node_update>;
template<class value, class cmp = less_equal<value> >
using ordered_multiset = tree<value, null_type, cmp, rb_tree_tag, tree_order_statistics_node_update>;
template<class key, class value, class cmp = less<key> >
using ordered_map = tree<key, value, cmp, rb_tree_tag, tree_order_statistics_node_update>;

/// find_by_order()
/// order_of_key()
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
inline int randll(int l = INT_MIN, int r = INT_MAX) {
    return uniform_int_distribution<int>(l, r)(rng);
}
const int INF = 1e9, MOD = 1e9 + 7; /// think
const ll LINF = 1e18;


const int dx[] = {0, 0, 1, -1}, dy[] = {1, -1, 0, 0};
inline bool inside (int x, int y, int n, int m) {
    return 0 <= x && 0 <= y && x < n && y < m;
}

template<class T> bool umin (T &a, T b) {return a > b ? (a = b, true) : false; }
template<class T> bool umax (T &a, T b) {return a < b ? (a = b, true) : false; }


main()
{
    ios::sync_with_stdio(0);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n, m;
    cin >> n >> m;
    map <int, int> nice;
    for (int i = 0, a, b; i < m; i++) {
        cin >> a >> b;
        --a;
        if (nice.count(a)) {
            if (nice[a] != b) {
                cout << "-1\n";
                rr;
            }
        }
        nice[a] = b;
    }
    if (nice.count(0) && nice[0] == 0) {
        if (sz(nice) > 1 || n > 1) {
            cout << "-1\n";
            rr;
        }
        cout << "0\n";
        rr;
    }
    if (n == 1 && m == 0) {
        cout << "0\n";
        rr;
    }
    if (!nice.count(0)) nice[0] = 1;
    cout << nice[0];
    int mx = 0;
    for (auto &i : nice) umax(mx, i.x);
    for (int i = 1; i < n; i++) {
        if (!nice.count(i)) nice[i] = 0;
        cout << nice[i];
    }
    cout << '\n';
}

// 問題の URL を書いておく
// 

#include <algorithm>
#include <array>
#include <bitset>
#include <cmath>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <vector>

using namespace std;

//#define ENABLE_PRINT

#if defined(ENABLE_PRINT)

#define Print(v) \
do {\
    cout << #v << ": " << v << endl; \
}while(0)

#define PrintVec(v) \
do {\
    for(int __i = 0; __i < v.size(); ++__i) \
    { \
        cout << #v << "[" << __i << "]: " << v[__i] << endl; \
    }\
}while(0)

#else

#define Print(v) ((void)0)
#define PrintVec(v) ((void)0)

#endif

#define rep(i, n) for(int i = 0; i < (int)(n); ++i)

using ll = int64_t;

int main(int, const char**)
{
    int n, m;
    cin >> n >> m;
    auto b = m / n;
    int ans = 1;
    for(int i = 1; i * i <= m; ++i)
    {
        if(m % i == 0)
        {
            int dd[] = {i, m / i};
            for(auto d : dd)
            {
                if(d <= b)
                {
                    ans = max(ans, d);
                }
            }
        }
    }
    cout << ans << endl;
    return 0;
}
