#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

#define RREP(i,s,e) for (i = s; i >= e; i--)
#define rrep(i,n) RREP(i,n,0)
#define REP(i,s,e) for (i = s; i < e; i++)
#define rep(i,n) REP(i,0,n)
#define INF 100000000

typedef long long ll;

int n;

void mult(vector<vector<int>> a, vector<vector<int>> b, vector<vector<int>>& c) {
    int i, j, k;
    rep (i,n) rep (j,n) {
        c[i][j] = 0;
        rep (k,n) {
            c[i][j] += a[i][k] * b[k][j];
        }
    }
}

int main() {
    int i, k;
    vector<vector<int>> ini, mat;
    cin >> n >> k;
    ini.resize(n);
    mat.resize(n);
    rep (i,n) {
        ini[i].resize(n);
        ini[i][i] = 1;
        mat[i].resize(n);
        mat[i][i] = 1;
    }
    rep (i,k) {
        int x, y;
        cin >> x >> y;
        swap(ini[x-1],ini[y-1]);
    }
    bool ok;
    int ans = 0;
    do {
        ok = true;
        mult(ini,mat,mat);
        rep (i,n) ok &= mat[i][i] == 1;
        ans++;
    } while (!ok);
    cout << ans << endl;
    return 0;
}