#include <iostream>
#include <fstream>

using namespace std;

#define MAX 2000000000

int f(int n){
    int rez=0;
    for(int i=5;i<=n;i*=5)
        rez+=n/i;

    return rez;
}


int main()
{
    ifstream in("fact.in");
    ofstream out("fact.out");

    int p;

    in>>p;

    if (p==0){
        out<<1;
        return 0;
    }

    for (int i=2;i<=MAX;i++){
        if (f(i) == p ){
            out<<i;
            return 0;
        }
    }


    out<<-1;
    in.close();
    out.close();
    return 0;
}