#include<bits/stdc++.h>
using namespace std;
#define ll long long
ll js(ll n,ll m)
{
	if(n == 1) return 0;
	if(m * 3 + 2 < n)
	{
	    ll k = 0;
	    while(n > m * 3 + 2)
	    {
	        n -= m * 2;
	        k ++;
	    }
	    return js(n,m) + k;
	}
	return js((n - 1) / 3 + 1,m) + 1;
}

int main()
{
	ll n,m;
	cin >> n >> m;
	cout << js(n,m) << endl;
	return 0;
 } 

Subtask #4 3TLE 1WA 求调