#include <iostream>
#include <fstream>

using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");

int fact( int a)
{
    int nr=0;
    while(a>=5)
    {
        nr+=a/5;
        a/=5;
    }
    return nr;
}

int main()
{
    int c, i, a=1<<28, r=0;
    in>>c;
    while(a!=0)
    {
        if(fact(r+a)<c)
            r+=a;
        a/=2;
    }
    r++;
    if(fact(r)==c)
        out<<r;
    else
        out<<-1;
    return 0;
}