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

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

int N,K;
bool isok(vector<int> a) {
    REP(i,a.size()) {
        if (a[i] != i) return false;
    }
    return true;
}
signed main()
{
    cin >> N>>K;
    vector<int> amida(N);
    REP(i,N) amida[i] = i;
    vector<int> x(K);
    int y;
    REP(i,K) {
        cin >> x[i] >> y;
        swap(amida[x[i]-1], amida[x[i]]);
    }
    int cnt = 0;
    vector<int> tmp(N);
    REP(i,N) tmp[i] = i;
    while(true) {
        cnt++;
        vector<int> tmp2(N);
        REP(i,N) {
            tmp2[i] = tmp[amida[i]];
        }
        if (isok(tmp2)) break;
        tmp = tmp2;
    }
    cout << cnt << endl;
    return 0;
}