#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>

#include<vector>

#define INF 999999
using namespace std;
int main(){
    double high,Y,i;
    while(~scanf("%lf",&high)){
        int F=1;
        i=high/9.8;
        Y=4.9*(i*i);
        for(;;){
            if(Y<=0)break;
            Y-=5;
            F++;
        }
        cout<<F<<endl;
    }
    return 0;
}