#include <iostream>
#include <fstream>

using namespace std;

unsigned long putere(unsigned n) {
    unsigned long k=1;
    for(int i=0;i<n;i++)
        k=k*10;
    return k;
}

unsigned long factorial(unsigned n) {
    if(n==0){
        return 1;
    }
    else
        return n*factorial(n-1);
}

int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    unsigned long n,k=0,i=1;
    f>>n;
    while(k==0)
        {
        if(factorial(i)%putere(n)==0)
            {f<<i;
            k=1;
            break;
            }
        i++;
        }
    if(k==0)
        g<<k;
    return 0;
}