#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 = 1;
		while(1){
			if( y <= n*5-5 ){
				printf("%d\n", n);
				break;
			}
			n++;
		}
	}
	
	return 0;
}