#include <iostream>
#include <fstream>


using namespace std;

long pow5(long);
int main()
{
    long p;
    long i,n,x;
    n = 1;
    i = 1;
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    fin >> p;
    while (p > 0){
        n = i * 5;
        x = pow5(i);
        p = p -x -1;
        i++;
    }

    if (p == 0)
        fout << n;
    else fout << -1;

    return 0;
}

long pow5(long x){
    long exp = 0;
    while (x % 5 == 0){
        exp++;
        x = x/5;
    }
    return exp;
}