#include <fostream>

using namespace std;

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

int main()
{
    int n;
    fin >> n;

    if(n == 0){
        fout << 1;
        return 0;
    }

    int nr5 = 0, rez = 1;
    while(nr5 < n){
        int c = rez;
        while(c % 5 == 0){
            c /= 5;
            nr5++;
        }
        rez++;
    }

    rez--;

    if(nr5 == n){
        fout << rez;
    }else if(nr5 > n){
        fout << -1;
    }
}