#include<iostream>
using namespace std;

int main(void){

    int ans;
    double N;
    double v,t;
    
    while(cin >> v){

        t = v / 9.8;

        N = (4.9 * t * t + 5) / 5;

        if(N -(int)N > 0.50){
            ans = (int)(N + 1);
        }else{
            ans = (int)N;
        }
        cout << ans << endl;
    }


    return 0;
}