#include <iostream>
#include <fstream>

using namespace std;

unsigned long cifre5(unsigned long long a){

    unsigned long k=0;
    while(a%5==0){
        a=a/5;
        k++;
    }
    return k;
}

int main()
{
    ifstream in("fact.in");
    ofstream out ("fact.out");
    unsigned long long n,p,k=0,i;
    in>>p;
    for(i=5;k<p;i=i+5){
        k=k+cifre5(i);
    }
    if(k==p) out<<i-5;
    else out<<-1;
    return 0;
}