#include <iostream>
using namespace std;
//ifstream fin("flip.in");
//ofstream fout("flip.out");
int p,nr,nrz,pr;



int main () {
    cin>>p;
    pr=1;
    if (p==0)
        cout<<1;
    else {
        while (nrz!=p) {
            nr++;
            pr*=nr;
            if (pr%10==0) {
                nrz++;
                pr/=10;
            }


        }
        cout<<nr;
    }
    return 0;
}