#include    <iostream>
#include    <fstream>

using namespace std;

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

int P,N,nr;
int main()
{
    fin>>P;
    if (P<0) N=-1;
    else
    do
    {
        N++;
        int c=N;
        while(c%5==0)
        {
            c/=5;
            nr++;
        }
    }
    while(nr!=P);
    fout<<N;
    return 0;
}