Buggy python submission (verdict: Time Limit Exceeded):
import sys
def LI(): return [int(x) for x in sys.stdin.readline().split()]
def II(): return int(sys.stdin.readline())
def LS(): return sys.stdin.readline().split()
sys.setrecursionlimit(10**7)
INF = 10 ** 18
MOD = 10 ** 9 + 7
def LI_(): return [int(x) - 1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def SI(): return input()
YN = lambda b: print('YES') if b else print('NO')
yn = lambda b: print('Yes') if b else print('No')

from scipy.misc import comb

def main():
    N, M, K = LI()

    rows = M*M*sum([d * (N-d) for d in range(1, N)])
    cols = N*N*sum([d * (M-d) for d in range(1, M)])
    ans = (rows + cols) * comb(M*N-2, K-2, exact=True) % MOD

    print(ans)

main()

Fixed submission:
import sys
def LI(): return [int(x) for x in sys.stdin.readline().split()]
def II(): return int(sys.stdin.readline())
def LS(): return sys.stdin.readline().split()
sys.setrecursionlimit(10**7)
INF = 10 ** 18
MOD = 10 ** 9 + 7
def LI_(): return [int(x) - 1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def SI(): return input()
YN = lambda b: print('YES') if b else print('NO')
yn = lambda b: print('Yes') if b else print('No')

def cmb(n, r, mod):
    if ( r<0 or r>n ):
        return 0
    r = min(r, n-r)
    return g1[n] * g2[r] * g2[n-r] % mod

mod = 10**9+7 #出力の制限
N = 2*10**5
g1 = [1, 1] # 元テーブル
g2 = [1, 1] #逆元テーブル
inverse = [0, 1] #逆元テーブル計算用テーブル

for i in range( 2, N + 1 ):
    g1.append( ( g1[-1] * i ) % mod )
    inverse.append( ( -inverse[mod % i] * (mod//i) ) % mod )
    g2.append( (g2[-1] * inverse[-1]) % mod )

def main():
    N, M, K = LI()

    rows = M*M*sum([d * (N-d) for d in range(1, N)])
    cols = N*N*sum([d * (M-d) for d in range(1, M)])
    ans = (rows + cols) * cmb(M*N-2, K-2, MOD) % MOD

    print(ans)

main()

Buggy python submission (verdict: Runtime Error):
import sys
def LI(): return [int(x) for x in sys.stdin.readline().split()]
def II(): return int(sys.stdin.readline())
def LS(): return sys.stdin.readline().split()
sys.setrecursionlimit(10**7)
INF = 10 ** 18
MOD = 10 ** 9 + 7
def LI_(): return [int(x) - 1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def SI(): return input()
YN = lambda b: print('YES') if b else print('NO')
yn = lambda b: print('Yes') if b else print('No')

from scipy.special import comb

def main():
    N, M, K = LI()

    rows = M*M*sum([d * (N-d) for d in range(1, N)])
    cols = N*N*sum([d * (M-d) for d in range(1, M)])
    ans = (rows + cols) * comb(M*N-2, K-2, exact=True) % MOD

    print(ans)

main()

Fixed submission:
import sys
def LI(): return [int(x) for x in sys.stdin.readline().split()]
def II(): return int(sys.stdin.readline())
def LS(): return sys.stdin.readline().split()
sys.setrecursionlimit(10**7)
INF = 10 ** 18
MOD = 10 ** 9 + 7
def LI_(): return [int(x) - 1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def SI(): return input()
YN = lambda b: print('YES') if b else print('NO')
yn = lambda b: print('Yes') if b else print('No')

def cmb(n, r, mod):
    if ( r<0 or r>n ):
        return 0
    r = min(r, n-r)
    return g1[n] * g2[r] * g2[n-r] % mod

mod = 10**9+7 #出力の制限
N = 2*10**5
g1 = [1, 1] # 元テーブル
g2 = [1, 1] #逆元テーブル
inverse = [0, 1] #逆元テーブル計算用テーブル

for i in range( 2, N + 1 ):
    g1.append( ( g1[-1] * i ) % mod )
    inverse.append( ( -inverse[mod % i] * (mod//i) ) % mod )
    g2.append( (g2[-1] * inverse[-1]) % mod )

def main():
    N, M, K = LI()

    rows = M*M*sum([d * (N-d) for d in range(1, N)])
    cols = N*N*sum([d * (M-d) for d in range(1, M)])
    ans = (rows + cols) * cmb(M*N-2, K-2, MOD) % MOD

    print(ans)

main()