#include <iostream>
#include <fstream>
#include <math.h>
using namespace std;
ifstream fin("fact.in.in");
ofstream fout("fact.out");
long long int p;
void solve()
{
    unsigned long long int ni=1;int j=1;
   while(true) {
        ni*=j;
        if(ni % int(pow(10,p)) == 0) {
            break;
        }
        j++;
   }
   fout<<j;
}
int main()
{
    fin>>p;
    solve();
}