#include <bits/stdc++.h> #include <atcoder/all> using namespace std; using namespace atcoder; typedef int64_t lint; #define rep(i, n) for(int i=0; i<n; i++) #define repx(i, l, n) for(int i=l; i<n; i++) #define all(v) v.begin(), v.end() #define show(x) cout << #x << ": " << x << endl; #define list(x) cout << #x << ": " << x << " "; #define pb push_back using vi = vector<lint>; using vvi = vector<vector<lint>>; template<class T> inline void vin(vector<T>& v) { rep(i, v.size()) cin >> v.at(i); } template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; } template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; } template<class T> inline void drop(T x) { cout << x << endl; exit(0); } template<class T> void vout(vector<T> v) { rep(i, v.size()) { cout << v.at(i) << ' '; } cout << endl; } constexpr lint LINF = LLONG_MAX/2; using pint = pair<lint, lint>; using vp = vector<pint>; int main() { lint N, M; cin >> N >> M; vp v(M); lint a=0, b=0, c=0, x, y, z; rep(i, M) { cin >> x >> y; v[i] = {x, y}; } rep(i, N+1) { bool f = true; rep(j, M) { tie(x, y) = v[j]; if ((i-y)%x != 0) { f = false; break; } } if (f) drop(i); } std::cout << "NaN" << '\n'; }