#include <iostream>
#include <fstream>
using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");

int mere(int n)
{
  int s=0;
  for(int i=5;i<=n;i*=5)
    s = s + n/i;
  return s;
}



int main()
{
  int n,p;
  in>>p;
  bool g = 0;

  int st =0, dr = 1e9;

  while(st <= dr)
  {
    int mid = (st+dr)/2;
    int a = mere(mid);
    if( a == p) g=1;
    if( a >= p) dr = mid-1;
    else st = mid+1;
  }
  if(p==0)  out<<1;
  else
  if(g) out<<dr+1;
  else out<<-1;


}