#include <fstream>

using namespace std;
int nr0 (int n){
  int nr0 = 0;
  while (n >= 5){
    nr0+= n/5;
    n/= 5;
  }
  return nr0;
}
int main()
{
    ifstream cin("fact.in");
    ofstream cout ("fact.out");
    int p;
    cin >> p;
    int r = 0;
    int pas = 1 << 28;
    while (pas != 0){
      if (nr0(r + pas) < p){
        r+= pas;
      }
      pas/= 2;
    }
    cout << r + 1;
    return 0;
}