sr=input().split()
M=int(sr[0])
N=int(sr[1])
a=[]
a.append(0)
for i in range(1,N+1):
    if(i==1):
        a.append(1)
    elif(i==2):
        a.append(1)
    else:
        a.append(a[i-2]+a[i-1])
print(a[N-M+1])
/**************************************************************
	Problem: 1368
	User: admin
	Language: Python
	Result: Accepted
	Time:143 ms
	Memory:34480 kb
****************************************************************/