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

int main(void){
	
	while (true){
		double v,t,y;
		cin>>v;
		if (cin.eof()) break;
		t = v/9.8;
		y = v/2*t;
		int h = ceil(y/5)+1;
		cout<<h<<endl;
	}
	return 0;
}