#include <fstream>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");

int main()
{
    int n,p,k=25;
    in>>p;
    if(p==0)out<<1;
    else {
        n=p*5;
        while(n>=k) {
            n-=n/k*5;
            if(n%k!=0)n+=5;
            k*=5;
        }
        k=5;
        int s=0;
        while(k<=n) {
            s+=n/k;
            k*=5;
        }
        out << ((s==p) ? n : -1);
    }
    return 0;
}