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

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

int verif(long long q)
{   int k=0;
    long long aux=q;
    while(aux%10==0)
        {k++;aux=aux/10;}
    if(k==p) return 1;
    else return 0;
}

int main()
{   int k=0;int z;
    f>>p; long long fact=1;
    for(long long i=2;i<9999999999;i++)
        {fact=fact*i;
        if(verif(fact))
            {o<<i<<endl; break;}

        }
        return 0;
}