#include <iostream>
using namespace std;

int main(){
	double v,y,n;
	double t=0;
	while(cin >> n){
		for(t=1;t*9.8<n;t++);
		t = t*t*4.9/5.0;
		if(t<1)cout << 1 << endl;
		else cout << (int)t << endl;
	}
}