#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for (int i=0; i<n; i++)
#define pb push_back
typedef long long ll;

int main() {
    cin.tie(0); ios::sync_with_stdio(false);
    
    int N, M; cin >> N >> M;
    vector<ll> rs, ms;
    rep(i, M) {
        ll Bi, Ci; cin >> Bi >> Ci;
        ms.pb(Bi);
        rs.pb(Ci);
    }
    
    pair<ll, ll> res = crt(rs, ms);
    if (res.first==0 && res.second==0) cout << "NaN" << endl;
    else {
        if (res.first>N) cout << "NaN" << endl;
        else cout << res.first << endl;
    }
}