#include<stdio.h>


int main(void){
	
	double v;
	
	while(scanf("%lf", &v) != EOF){
		double t = v/9.8;
		double y = 4.9*t*t;
		
		int n = y/5+2;
		if(y <= 9.8)n--;
		if((int)y == y)n--;
		
		printf("%d\n", n);
	}
	
	return 0;
}