출처 | https://www.acmicpc.net/problem/9184
import sys
input = sys.stdin.readline
dp = [[[0] * 21 for i in range(21)] for j in range(21)]
def w(a,b,c):
if a<=0 or b<=0 or c<=0:
return 1
if a>20 or b>20 or c>20:
return w(20,20,20)
if dp[a][b][c]:
return dp[a][b][c]
if a<b<c:
dp[a][b][c] = w(a,b,c-1) + w(a,b-1,c-1) - w(a,b-1,c)
return dp[a][b][c]
else:
dp[a][b][c] = w(a-1,b,c) + w(a-1,b-1,c) + w(a-1,b,c-1) -w(a-1,b-1,c-1)
return dp[a][b][c]
while 1:
a,b,c = map(int, input().split())
if a==-1 and b == -1 and c == -1:
break
ans = w(a,b,c)
print('w(%d, %d, %d) = %d' %(a,b,c, ans))