#include <iostream>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <vector>

using namespace std;

int main(){
	double v;

	while(cin >> v){
		double m = (v*v)/(4*4.9);
		for(int i = 0; i < 10000; i++){
			if(m <= i*5-5){
				cout << i << endl;
				break;
			}
		}
	}

	return 0;
}