#include<iostream>
#include<string>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int main(void){
    double a;
	while(cin>>a){


	double v,t,y;
	t=a/9.8;
    y=4.9*t*t;
    for(int i=0;i<10000000;i++){
        if(y<=5*i-5){
            cout<<i<<endl;
            break;
        }
    }
	}
	return 0;
}