#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
    double x;
    int i=1,m=2.0,z,j,y;
	cin>>x;
	if(x==m) cout<<x/m;
	while(x>m)
	{
		for(j=2;j<=10000000;j++)
		{
			m=m*0.98;
		}
		for(y=1;y<=10000000;y++)
		{
			z+=m;
			i++;
		}
		if(z==x)
			{
				cout<<i;
			}
	}
	return 0;
}