#include <stdio.h>
 
int main(void){
	float v,t,y,n1;
	int n;
	while(scanf("%f",&v)!=EOF){
		fflush(stdin);
    	t=v/9.8;
    	y=4.9*t*t;
    	n=0;
    	n1=(5+y)/5;
    	while(n<n1){
    		n=n+1;
    	}
		printf("%d\n",n);
    }
	return 0;
}


//debug for alfa