#include<iostream>
#include<map>
#include<cstdio>
#include<cstring>
#include<string>
using namespace std;
int main(){
	double a,b,c;
	int d,e;
	while(scanf("%lf",&c)!=EOF){
		a=c/9.8;
		b=(a*a*4.9+5)/5;
		d=(a*a*4.9+5)/5;
		if(b!=d)d++;
		printf("%d\n",d);
	}
}