#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

int dt[45][2][8], n, k;

int dp(int x, int s, int stat)
{
    if( s > 1 ) return 0;
    if( x == n+1 ) return 1;
    if( dt[x][s][stat] ) return dt[x][s][stat];
    if( x == k ) return dt[x][s][stat] = dp(x+1, s, (stat|0x2)>>1);
    if( x > 1 && !(stat&(0x1)) ) dt[x][s][stat]+=dp(x+1, s, (stat|0x1)>>1);
    if( !(stat&(0x2)) ) dt[x][s][stat]+=dp(x+1, s, (stat|0x2)>>1);
    if( x < n && x+1 != k && !(stat&(0x4)) ) dt[x][s][stat]+=dp(x+1, s, (stat|0x4)>>1);
    dt[x][s][stat]+=dp(x+1, s+1, (stat>>1));
    return dt[x][s][stat];
}

int main()
{
    freopen(".10.in","r",stdin);
    freopen(".10.out","w",stdout);
    scanf("%d%d", &n, &k);
    printf("%d", dp(1,0,0));
}