#include <cstdio>
#include <cmath>

using namespace std;

inline double sq(double x) {
  return x * x;
}

int main() {
  double v;
  while (scanf("%lf", &v) == 1)
    printf("%d\n", int(ceil(4.9 * sq(v / 9.8) / 5.0)) + 1);
  return 0;
}