870 B | 870 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
# sys.setrecursionlimit(10**7)
BLANK = " "
# inp = input
inp = lambda : sys.stdin.readline().rstrip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def gcd(a, b): return gcd(b, a % b) if b > 0 else a
def lcm(a, b): return a * b // gcd(a, b)
def solve():
d = [[0] * 40 for _ in range(40)]
d[0][0] = 1
for i in range(1, 31):
for j in range(i + 1):
s = max(0, j - 1)
d[i][j] = sum(d[i - 1][s:j + 1])
r, c, w = mii()
r -= 1
c -= 1
ans = 0
for i in range(w):
for j in range(i + 1):
y = r + i
x = c + j
ans += d[y][x]
p(ans)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()