#include<cstdio>

int main(){
  double target;
  while(scanf("%lf",&target)>0){
    double y = 4.9*target*target/(9.8*9.8);
    for(int n=1;;n++){
      if(5*n-5 >= y){
	printf("%d\n",n);
	break;
      }
    }
  }
}