memo = [0]
memo = memo*10000
def pas(x,y):
global memo
if x != 1 and y!=1:
memo[x][y]=memo[x-1][y]+memo[x][y-1]
else:
memo[x][y]=1
return memo[x][y]
def rec(r,c,x,y):
global memo
if y!=c and x!=r:
if x!=r:
x = x+1
pas(x,y)
return rec(r,c,x,y)
else:
y = y+1
pas(x,y)
return(r,c,x,y)
else:
return memo[x][y]
r,c = input().split()
x = 0
y = 0
x = int(x)
y = int(y)
r = int(r)
c = int(c)
print(rec(r,c,x,y))