#include <fstream>

using namespace std;

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

int p, n, r, c, suma, st, dr, mid, w, v[100000];

int main (){

      fin>>p;

      st = 1; dr = p*5;

      while (st <= dr) {
            r = (st + dr)/2;
            c = 5;
            suma = 0;
            while (c <= r) {
                  suma += r/c;
                  c *= 5;
                }
            if (suma >= p)
                  dr = r;
            else
                  st = r;
      }
      c = 5;
      suma = 0;
      while(c<=st){
            suma = suma + st/c;
            c = c*5;
      }

      if(suma != p)
        fout<<-1;
      else
        fout<<st;
      return 0;
}