#include<stdio.h>
int main(){
	double v;
	while(~scanf("%lf",&v)){
		double t,x;
		t=v/9.8;
		x=4.9*t*t;
		for(int n=408;n>=0;n--){
			if(x>(n*5)){
				printf("%d\n",(n+2));
				break;}}}
	return 0;}
