#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
int main(){
double n;
while(scanf("%lf",&n)!=EOF){
n=n/9.8;
n=n*n*4.9;
int i;
for(i=1;i*5-5<n;i++);
cout<<i<<endl;
}
return 0;
}