#include <iostream>
using namespace std;
int main(){
	double v;
	while(cin>>v){
		int n;
		double t = v/9.8;
		double y = 4.9*t*t;
		for(int i=0;;i++){
			if(5*i-5>y){
				n=i;
				break;
			}
		}
		cout<<n<<endl;
	}
	return 0;
}