#include <iostream>
using namespace std;

int main(){
	double v;
	while( ~scanf("%lf", &v) ){
		double t, y;
		t = v / 9.8;
		y = 4.9 * t * t;
		int floar = (y + 5) / 5 + 1;
		cout << floar << endl;
	}
}