#include<string>
#include<cmath>
#include<iostream>

using namespace std;
 
int main(){
	double v;

	while(cin >> v){
		int n=1;
		double t,y;

		t=v/9.8;
		y=4.9*t*t;

		while(5*(n-1)<y) n++;

		cout<<n<<endl;
	}
    return 0;
}