#include <iostream>
#include <fstream>

using namespace std;

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

int factorialzero(int n)
{
    int z=0,p=5;
    while(p<=n)
    {
        z=z+n/p;
        p=p*5;
    }
    return z;
}

int main()
{
    int i,j=0,n,k=1,aux,v,p=-1;
    fin>>n;
    for(i=1;i<=100000;i++)
    {
        if(factorialzero(i)==n)
        {
            p=i;
            fout<<p;
            return 0;
        }
    }
}