#include<iostream>
#include<cmath>
using namespace std;

int main(){
	double v;
	while(cin>>v){
		double t=v/9.8;
		double y=4.9*t*t;
		int n=(((y+5)/5)*10+9)/10;
		
		/*for(int i=0;0<y;i++){
			y-=5;
			c++;
		}*/
		cout<<n<<endl;
	}
}