#include<iostream>
using namespace std;

int main(void){

    int i = 0;;
    double v,y;
    
    while(cin >> v){

        y = v * v / 19.6;

        while(1){

            if((5 * i - 5 ) > y){
                cout << i << endl;
                break;
            }
            i++;
        }
       
    }
    return 0;
}