#include <bits/stdc++.h>

using namespace std;


ifstream fin("pascal.in");
ofstream fout("pascal.out");

int v[5000005],r,d;

void Formare_V()
{
    int i;

    v[0]=0;

    for(i=1;i<=r+1;i++)
        if(i%d==0) v[i]=v[i-1]+1;
        else v[i]=v[i-1];
}


///i!/(i-j)!*j!
///if(v[i-j]+v[j]<v[i]) nr+=2;

int Solutie()
{
    int i,nr=0;

    for(i=1;i<=r/2;i++)
        if((v[r-i]+v[i])<=v[r]) nr+=2;
    return nr;
}

int main()
{
    fin>>r>>d;

    Formare_V();

    fout<<Solutie();

    return 0;
}