#include <fstream>

using namespace std;
int zero (int n)
{if(n==0) return 0;
 return n /5+zero(n/5);

    }


int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    int n=9,p,ok=1;
    f>>p;
    while(p!=zero(n))
    {
        n=n+1;

    }
    if(zero(n)==p)
    g<<n;
    else
    g<<"-1";

    return 0;
}