#include <bits/stdc++.h>

using namespace std;

int n;

int eular(int n){
  int ret = 1, i;
  for(i = 2; i * i <= n; i++){
    if(n%i == 0){
      n/=i;
      ret *= i - 1;
      while(n%i==0){
        n/=i;
        ret*=i;
      }
    }
  }
  if(n>1){ret*=n-1;}
  return ret;
}

int main() {
  scanf("%d", &n);
  if (n == 2) {
    printf("1\n");
    return 0;
  }
  int nn = n;
  vector<int> vp;
  int ff = 1;
  for (int i = 2; i * i <= nn; ++i) {
    if (nn % i == 0) {
      vp.push_back(i);
      int cnt = 0;
      while (nn % i == 0) {
        nn /= i;
        cnt++;
      }
      if (cnt > 1) {
        ff = 0;
      }
    }
  }
  if (!ff) {
    printf("-1\n");
    return 0;
  }
  if (nn > 1)
    vp.push_back(nn);
  int lcm = 1;
  for (int i = 0; i < vp.size(); ++i) {
    int gg = __gcd(vp[i] - 1, lcm);
    lcm = lcm / gg * (vp[i] - 1);
  }
//  printf("%d\n", lcm);
  int i = 1;
  lcm = min(lcm, eular(n));
  if (__gcd(n, lcm) != 1) {
    puts("-1");
    return 0;
  }
  n %= lcm;
  long long t = n;
  while (1) {
    if (t == 1) break;
    t = t * n % lcm;
    i++;
  }
  printf("%d\n", i);
  return 0;
}