/* DIU_HowCow */

#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <ctime>
#include <iomanip>

#define LLI long long
#define LLU unsigned long long
#define pi 2*acos(0.0)
#define MOD 10007

#define scan(x) scanf("%d",&x)


using namespace std;


int main()
{
    double v;
    while(scanf("%lf",&v) != EOF)
    {
        double t = v / (9.8) ;
        double y = t*t*( 4.9 );

        LLI flr = ceil( (y + 5) / 5 );

        printf("%lld\n",flr);
    }

	return 0;
}