#include<iostream>
using namespace std;
main(){
	double in;
	while(cin>>in){
		double t,y;
		int n;
		t=in/9.8;
		y=4.9*t*t;
		for(int i=1;;++i){
			if(5*i-5>y){
				n=i;
				break;
			}
		}
		cout<<n<<endl;
	}	
}