#include <iostream>
#include <fstream>

using namespace std;

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

int main()
{
    int i,p,c,j;
    in >> p;
    i=5;
    c=1;
    if(p==0){
        out << 1;
    }
    else{
       while(c!=p)
    {
        i=i+1;
        j=i;
        while(j%5==0){
            c=c+1;
            j=j/5;

        }
        if(c>p){
            i=-1;
            break;
        }
    }

    out << i;
    }


}