

#include<cstdio>
#include<iostream>
#include<math.h>
using namespace std;

int main(){

    double v,s,floorH;
    int i;
    while(cin>>v){
        s=(v/9.8)*(v/2);
        for(i=1;i;i++){
            floorH=5*i-5;
            if(floorH>=s){
                cout<<i<<endl;
                break;
            }
        }
    }

return 0;
}