#include <iostream>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <iomanip>
using namespace std;
int main()
{
	double s,d = 2,sum = 0;
	int cnt = 1;
	cin >> s;
	sum += d;
	while(1)
	{
		sum += d * 0.98;
		cnt++;
		if(sum >= s)
		{
			break;
		}
	}
	cout << cnt;
	return 0;
}