#include <stdio.h>
#include <fstream>
#include <iostream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int main()
{
    int qwe=0,zxc;
    unsigned a;
    fin>>a;
    if ((a%6)==(5%6)){
        fout<<-1;
    }
    else{
    zxc=a*5;
        while (zxc/25!=0){
            qwe+=1;
        zxc/=25;
        }
        fout<<(a-qwe)*5;
    }
    
    return 0;
}