#include <iostream>
#include <fstream>
#include <math.h>
using namespace std;

int P;

int fact(int N)
{
    int nullak=0;
    while(N != 0)
    {
        nullak += N/5;
        N /= 5;
    }
    return nullak;
}


int binker(int a, int b, int x)
{
    if(a==b)return a;
    int p=(a+b)/2;
    if(fact(p) < P) return binker(p+1,b,x);
    else return binker(a,p,x);
}

int main()
{
    int a=5;
    ifstream in("fact.in");
    ofstream out("fact.out");
    in>>P;
    if(P==a or (P-5)/2==a) out<<-1;
    else out<<binker(1, 1000000000, P);
    return 0;
}