#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    int n, v[100000001];
    int k=0, c=0;
    f >> n;
    for(int i=0; i<=n; i++)
    {
        v[i]=k;
        k+=5;
        c++;
        if(c==5) {i++; c=0;}
    }
    if(v[n]==0) g << -1;
    else g << v[n];
}