#include <iostream>
#include <cmath>
using namespace std;

int main() {
  int i;
  double v,vmin;
  while(cin >> vmin) {
    i=1;
    while(1) {
      v = 9.8 * sqrt((5*i-5)/4.9);
        if(v >= vmin) break;
        i++;
    }
    cout << i << endl;
  }
}