#include<iostream>
#include<cmath>
#include<cstdlib>
#include<cstdio>

using namespace std;

int main(void){
	double sp;
	while(cin >> sp){
		double t=(double)sp/9.8;
		t=pow(t,2);
		t*=4.9;
		int f=0;
		while(1){
			if((f-1)*5>t){
				printf("%d\n",f);
				break;
			}
			f++;
		}
	}
    return 0;
}