#include <fstream>

using namespace std;

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

int main() {
    int k,p,n,pow;

    f>>p;
    n = 4*p, k = 0; pow = 5;
    while(n/pow) k += n/pow, pow *= 5;
    n = 5*(n/5+1);
    do {
        pow = 5, k = 0;
        while(n/pow) k += n/pow, pow *= 5;
        n += 5;
    } while(k < p);
    n -= 5;
    if(p == 0) g<<1;
    else {
        if(k == p) g<<n;
        else g<<-1;
    }
    return 0;
}