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

int main(){
	double v, y;
	while(cin >> v){
		y = 4.9 * pow(v / 9.8, 2);
		int n = 0;
		while(n++)if(y <= 5*n-5)break;
		cout << n << endl;
	}
	return 0; 
}