#include <iostream>

using namespace std;

int main(){
	double v,t,y;
	int n;
	while(cin>>v){
		n=1;
		t=v/9.8;
		y=4.9*(t*t);
		while(true){
			n++;
			if(5*n-5>y){
				cout<<n<<endl;
				break;
		}
	}
}
}