#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int main()
{
    int n, i=5;
    long long nr=0;
    f >> n;
    while(nr<n)
    {
        int k=0, p=i;
        while(p%5==0)
        {
            k++;
            p/=5;
        }
        nr+=k;
        i+=5;
    }
    if(nr!=n) g << "-1";
    else g << i-5;
}