#include <bits/stdc++.h>
using namespace std;
int const N = 1e5 + 13;
int n, m;
set<int> e[N];
set<pair<int, int> > q;
int p[N];
int tin[N], cnt, w[N], ans;
int gcd(int a, int b) { return (!a ? b : gcd(b % a, a)); }
void init() {
  for (int i = 0; i < N; ++i) p[i] = i;
}
int find(int u) {
  if (p[u] == u) return u;
  return p[u] = find(p[u]);
}
void uni(int a, int b) {
  a = find(a);
  b = find(b);
  if (a == b) return;
  if (e[a].size() < e[b].size()) swap(a, b);
  for (int to : e[b]) e[a].insert(find(to));
  p[b] = a;
  e[b].clear();
}
void print(int ans) {
  printf("%d\n", ans);
  exit(0);
}
pair<int, int> getMax() {
  auto it = q.end();
  --it;
  pair<int, int> res = (*it);
  return res;
}
void merge(int id) {
  if (id != find(id)) return;
  vector<int> ver;
  for (int v : e[id]) ver.push_back(find(v));
  e[id].clear();
  for (int i = 0; i < ver.size(); ++i) {
    int pi = find(ver[i]);
    q.erase(make_pair(e[pi].size(), pi));
  }
  for (int i = 1; i < ver.size(); ++i) uni(ver[i], ver[i - 1]);
  int lv = find(ver[0]);
  id = find(id);
  e[id].insert(lv);
  q.insert(make_pair(e[lv].size(), lv));
  q.insert(make_pair(e[id].size(), id));
  if (e[id].find(id) != e[id].end()) print(1);
}
void compress() {
  for (int i = 0; i < n; ++i) {
    q.insert(make_pair(e[i].size(), find(i)));
  }
  while (true) {
    pair<int, int> cur = getMax();
    if (cur.first < 2) return;
    q.erase(cur);
    merge(cur.second);
  }
}
void dfs(int u) {
  w[u] = 1;
  tin[u] = cnt;
  ++cnt;
  for (int to : e[u]) {
    int vt = find(to);
    if (!w[vt])
      dfs(vt);
    else if (w[vt] == 1) {
      ans = gcd(ans, tin[u] - tin[vt] + 1);
    }
  }
  w[u] = 2;
  --cnt;
}
void solve() {
  init();
  scanf("%d %d", &n, &m);
  for (int i = 0; i < m; ++i) {
    int u, v;
    scanf("%d %d", &u, &v);
    --u;
    --v;
    if (u == v) print(1);
    e[u].insert(find(v));
  }
  compress();
  for (int i = 0; i < n; ++i)
    if (!w[find(i)]) dfs(find(i));
  if (ans == 0) ans = n;
  printf("%d\n", ans);
}
int main() {
  solve();
  return 0;
}
