#include<iostream>
using namespace std;
int main(){
    double v;
    while( cin >> v ){
        double t = v / 9.8;
        double y = 4.9 * t * t;
        int N = 1;
        while(1){
            if( (5 * N - 5) > y) break;
            N++;
        }
        cout << N << endl;
    }
}