#include <stdio.h>
#include <math.h>
int main(){
double v;
while(scanf("%lf",&v) != EOF){
double y=v*v/19.6;
int z=y;
if(y==z){
if(z%5==0){
	z=y/5+1;
printf("%d\n",z);
continue;
}
}
int q=y/5;
q += 2;
printf("%d\n",q);
}
return 0;
}