#include <iostream>
#include <vector>
#include <cstdio>
#include <string>
#include <queue>
#include <algorithm>
#include <cstring>

using namespace std;

typedef long long LL;

#define MAX_N 101
#define MAX_K 1001

int N, K;
int X[MAX_K], Y[MAX_K];

void Input(){

  cin >> N;
  cin >> K;

  for(int i = 0; i < K; i++){
    cin >> X[i] >> Y[i];
  }

}

bool ChangeFlag[MAX_N];
int List[2][MAX_N];

void ExecAmida(vector<int>& AmidaList){

  for(int k = 0; k < K; k++){
    int x = X[k], y = Y[k];
    x--; y--;
    swap(AmidaList[x], AmidaList[y]);
  }

}

int Solve(){

  vector<int> AmidaList;

  for(int i = 1; i <= N; i++){
    AmidaList.push_back(i);
    List[0][i-1] = i-1;
  }

  //MakeAmidaExec
  ExecAmida(AmidaList);

  vector<int> NextList;
  for(int i = 1; i <= N; i++){
    for(int j = 0; j < N; j++){
      if(AmidaList[j] == i){
	NextList.push_back(j);
	break;
      }
    }
  }

  //Debug
  /*
  for(int i = 0; i < N; i++){
    cerr << i << "->" << NextList[i] << endl;
  }
  */

  int ret = 0;
  while(true){
    ret++;
    bool flag = true;
    for(int i = 0; i < N; i++){
      int nextPos = NextList[i];
      List[ret%2][nextPos] = List[(ret-1)%2][i];
      if(List[ret%2][nextPos] != nextPos){
	flag = false;
      }
    }
    if(flag)
      break;
  }

  return ret;

}

int main(){

  Input();

  cout << Solve() << endl;

  return 0;

}