A = int(input())
B= int(input())
f = [1,2]
for i in range(3,A+1):
    if B>0:
        if i==3:
            f.append(f[i-1]+f[i-2]+1)
        else:
            f.append(f[i-1]+f[i-2]+f[i-3])
        B-=1
    else:
        f.append(f[i-1]+f[i-2])
print(f[-1])


Test case:
A=4
B=1
Output expected=7
I got 6