#include<stdio.h>

double func(double v){
	
	double t,y;
	
	t=v/9.8;
	y=4.9*t*t;
	
	return y;
}


int main(void){
	
	int height,floor;
	double speed;
	
	while(scanf("%lf",&speed)!=EOF){
		floor=func(speed)/(double)(5-1);
	
		printf("%d\n",floor);
	}
	return 0;
}