There are H rows and W columns of white square cells.
You will choose h of the rows and w of the columns, and paint all of the cells contained in those rows or columns.
How many white cells will remain?
It can be proved that this count does not depend on what rows and columns are chosen.

-----Constraints-----
 - All values in input are integers.
 - 1 \leq H, W \leq 20
 - 1 \leq h \leq H
 - 1 \leq w \leq W

-----Input-----
Input is given from Standard Input in the following format:
H W
h w

-----Output-----
Print the number of white cells that will remain.

-----Sample Input-----
3 2
2 1

-----Sample Output-----
1

There are 3 rows and 2 columns of cells. When two rows and one column are chosen and painted in black, there is always one white cell that remains.

Difficulty: introductory

Starter code:

Solutions:
H, W = map(int, input().split())
h, w = map(int, input().split())
print((H-h) * (W-w))

H,W = map(int,input().split())
h,w = map(int,input().split())
print((H-h)*(W-w))

H,W = map(int,input().split())
h,w = map(int,input().split())
print(H*W-H*w-W*h+h*w)

H,W=map(int,input().split())
h,w=map(int,input().split())
print((H-h)*(W-w))

H, W = map(int, input().split())
h, w = map(int, input().split())

ans = max(0, H * W - h * W - H * w + h * w)
print(ans)

h,w = map(int,input().split())
x,y = map(int,input().split())

print((h-x)*(w-y))

H,W=map(int,input().split())
h,w=map(int,input().split())
print(H*W-(W*h+H*w-h*w))

H, W = map(int, input().split())
h, w = map(int, input().split())

print(H * W - (h*W + w*H - h*w))

def lcm(a, b):
    return a*b//math.gcd(a, b)

H, W = list(map(int, input().split()))
h, w = list(map(int, input().split()))
print(((H-h)*(W-w)))


H,W=map(int,input().split())
h,w=map(int,input().split())
print(H*W-H*w-W*h+w*h)

a,b =map(int,input().split())
c,d =map(int,input().split())
print((a-c)*(b-d))

H,W = list(map(int,input().split()))
h,w = list(map(int,input().split()))

print((H*W-W*h-H*w+w*h))


H,W=map(int,input().split())
h,w=map(int,input().split())
print(H*W-h*W-H*w+h*w)

H, W = map(int, input().split())
h, w = map(int, input().split())

ans = (H-h) * (W-w)
print(ans)

H1, W1 = map(int, input().split())
H2, W2 = map(int, input().split())

H=H1-H2
W=W1-W2

print(H*W)

H, W = map(int, input().split())
h, w = map(int, input().split())
print((H-h) * (W-w))

H,W = map(int,input().split())
h,w = map(int,input().split())
print((H-h)*(W-w))

H,W = map(int,input().split())
hh,ww = map(int,input().split())
print((H-hh)*(W-ww))

H,W=map(int,input().split())
h,w=map(int,input().split())
print(H*W-W*h-H*w+h*w)

H, W = map(int, input().split())
h, w = map(int, input().split())
print((H - h) * (W - w))

a, b = map(int, input().split())
c, d = map(int, input().split())
print((a - c) * (b - d))

H,W = map(int,input().split())
h,w = map(int,input().split())

print((H-h)*(W-w))

#入力:N,M(int:整数)
def input2():
	return map(int,input().split())

H,W=input2()
h,w=input2()

ans= (H-h)*(W-w)
print(ans) 

H, W = list(map(int, input().split()))
h, w = list(map(int, input().split()))
print(((H-h)*(W-w)))


n1, k1 = map(int, input().split())
n2, k2 = map(int, input().split())

print((n1-n2)*(k1-k2))

H,W = map(int,input().split())
h,w = map(int,input().split())

ans = H*W - (H*w+W*h) + (h*w)
print(ans)

H, W = list(map(int, input().split()))
h, w = list(map(int, input().split()))
print(((H - h) * (W - w)))


H, W = map(int, input().split())
h, w = map(int, input().split())

print(H*W-h*W-H*w+h*w)

H,W=map(int,input().split())
h,w=map(int,input().split())
print((H-h)*(W-w))

H,W=map(int,input().split())
h,w=map(int,input().split())
print(H*W-h*W-w*H+h*w)

H,W = map(int,input().split())
h,w = map(int,input().split())

print((H - h) * (W - w))

a,b = map(int,input().split())
h,w = map(int,input().split())

print((a - h) * (b - w))

H,W = map(int,input().split())
h,w = map(int,input().split())
print((H-h)*(W-w))

H, W = map(int, input().split())
h, w = map(int, input().split())

print((H - h) * (W - w))

H,W=list(map(int, input().split()))
h,w=list(map(int, input().split()))

print(((H-h)*(W-w)))


H1, W1 = map(int, input().split())
H2, W2 = map(int, input().split())
print((H1-H2)*(W1-W2))

H,W=map(int,input().split())
h,w=map(int,input().split())
print((H-h)*(W-w))

def mapt(fn, *args):
    return tuple(map(fn, *args))


def Input():
    return mapt(int, input().split(" "))


def main():
    H, W = Input()
    h, w = Input()
    print(H * W - ((H * w + W * h) - (h * w)))

main()

a,b = map(int,input().split())
c,d = map(int,input().split())
print((a-c)*(b-d))

H, W = list(map(int, input().split()))
h, w = list(map(int, input().split()))

print((H*W - (h*W + w*H - h*w)))


H,W=map(int,input().split())
h,w=map(int,input().split())
print((H-h)*(W-w))

H, W = map(int, input().split())
h, w = map(int, input().split())
print((H-h)*(W-w))

H, W = map(int, input().split())
h, w = map(int, input().split())
print(H*W - h*W - H*w + h*w)

H,W=map(int,input().split())
h,w=map(int,input().split())

HW=[]

for i in range(H):
  sublist=[]
  for j in range(W):
    sublist.append(0)
  HW.append(sublist)


# 行
for i in range(h):
  for j in range(W):
    HW[i][j]=1


# 列
for i in range(w):
  for j in range(H):
    if HW[j][i]==1: continue
    HW[j][i]=1

cnt=0

for i in range(H):
  for j in range(W):
    if HW[i][j]==0:
      cnt+=1

print(cnt)

a, b = list(map(int, input().split()))
a_l, b_l = list(map(int, input().split()))

ans = (a - a_l) * (b - b_l)
print(ans)


H,W=map(int,input().split())
h,w=map(int,input().split())
print(H*W-(H*w+W*h-h*w))

H, W = map(int, input().split())
h, w = map(int, input().split())

print((H-h) * (W-w))

H,W=map(int, input().split())   
h,w=map(int, input().split())   
print(H*W-(h*W+H*w-h*w))

a,b=map(int, input().split())
h,w=map(int, input().split())

print(a*b-(h*b+a*w-w*h))

"""
import numpy as np
import math
from numba import njit
from scipy.special import perm
from scipy.special import comb

#@njit('f8(i8,i8,i8,i8,f8[:,:,:])', cache=True)

def lcm(a, b):
    return a*b//math.gcd(a, b)

MOD = 10**9+7
"""

H, W = list(map(int, input().split()))
h, w = list(map(int, input().split()))
print(((H-h)*(W-w)))


H,W=list(map(int,input().split()))
h,w=list(map(int,input().split()))
print(H*W-h*W-w*H+h*w)

H,W = map(int,input().split())
h,w = map(int,input().split())
print((H-h)*(W-w))

H, W = map(int, input().split())
h, w = map(int, input().split())
print(H * W - h * W - w * H + h * w)

a,b = map(int,input().split())
c,d = map(int,input().split())
print((a-c)*(b-d))

H,W=list(map(int,input().split()))
h,w=list(map(int,input().split()))

print((H*W-h*W-H*w+h*w))


H, W=map(int, input().split(" "))
h, w=map(int, input().split(" "))

# print(H,W)
# print(h,w)

black=H*w+W*h-h*w

print(H*W-black)

x,y = map(int,input().split())
X,Y = map(int,input().split())
print((x-X)*(y-Y))

H, W = map(int, input().split())
h, w = map(int, input().split())
white = H*W
black = (W*h) + ((H-h)*w) 
print(white - black)

# import numpy as np
# import math

# from scipy.special import perm
# from scipy.special import comb

# from numba import njit
# @njit('f8(i8,i8,i8,i8,f8[:,:,:])', cache=True)

def lcm(a, b):
    return a*b//math.gcd(a, b)

MOD = 10**9+7


H, W = list(map(int, input().split()))
h, w = list(map(int, input().split()))
print(((H-h)*(W-w)))


a,b=map(int,input().split())
c,d=map(int,input().split())
print((a-c)*(b-d))


H,W=map(int,input().split())
h,w=map(int,input().split())
print((H-h)*(W-w))

#!/usr/bin/env python3

def main():
    H, W = list(map(int, input().split()))
    h, w = list(map(int, input().split()))
    print(((H - h) * (W - w)))


def __starting_point():
    main()

__starting_point()

h,w = map(int,input().split())
s,t = map(int,input().split())
print(h*w-s*w-t*h+s*t)

H,W = list(map(int,input().split()))
h,w = [int(i) for i in input().split()]
n = (H-h) * (W-w)
print(n)


H,W = map(int,input().split())
h,w = map(int,input().split())

seki = H * W
print(seki - (h*W + w*H - h * w))

h,w = map(int,input().split())
x,y = map(int,input().split())
print(h*w-w*x-h*y+x*y)

H, W = map(int, input().split())
h, w = map(int, input().split())
print((H-h)*(W-w))

H, W = map(int,input().split())
h, w = map(int,input().split())
print(H*W - (h*W+w*H - h*w))

H,W=map(int,input().split())
h,w=map(int,input().split())
print(H*W-h*W-H*w+h*w)

H, W = map(int, input().split())
h, w = map(int, input().split())

print(H*W - (h*W+w*H-h*w))

H,W=list(map(int,input().split()))
h,w=list(map(int,input().split()))
print(((H-h)*(W-w)))


H, W = map(int, input().split())
h, w = map(int, input().split())
print((H - h) * (W - w))

rows, columns = list(map(int, input().split()))
black_rows, black_columns = list(map(int, input().split()))

area = rows * columns
black_space = black_columns * rows + black_rows * columns - black_rows * black_columns

print((area - black_space))


h1, w1 = map(int, input().split())
h2, w2 = map(int, input().split())
print((h1 - h2) * (w1 - w2))

H,W=map(int,input().split())
h,w=map(int,input().split())
print(H*W-h*W-w*H+h*w)

a,b=map(int,input().split(" "))
c,d=map(int,input().split(" "))
print((a-c)*(b-d))

H,W=map(int,input().split())
h,w=map(int,input().split())
print((H-h)*(W-w))

import numpy as np
import math
from numba import njit
from scipy.special import perm
from scipy.special import comb

#@njit('f8(i8,i8,i8,i8,f8[:,:,:])', cache=True)

def lcm(a, b):
    return a*b//math.gcd(a, b)

MOD = 10**9+7

H, W = list(map(int, input().split()))
h, w = list(map(int, input().split()))
print(((H-h)*(W-w)))


a = list(map(int,input().split()))
b = list(map(int,input().split()))
print(((a[0]-b[0])*(a[1]-b[1])))


H, W = map(int, input().split())
h, w = map(int, input().split())
t = H * W
o = h*W + w*H
c = h*w
diff = o - c
print(t - diff)

H, W = map(int,input().split())
h, w = map(int,input().split())
print(H*W + h*w - H*w - W*h)

H, W = map(int, input().split())
h, w = map(int, input().split())

print((H - h) * (W - w))

H,W = map(int,input().split())
h,w = map(int,input().split())
print(H*W-h*W-H*w+h*w)

import numpy as np
import math
def lcm(a, b):
    return a*b//math.gcd(a, b)

H, W = list(map(int, input().split()))
h, w = list(map(int, input().split()))
print(((H-h)*(W-w)))


H, W = map(int, input().split())
h, w = map(int, input().split())

ans = H*W - h*W - w*(H-h)
print(ans)

H,W=list(map(int,input().split()))
h,w=list(map(int,input().split()))

ans=H*W-h*W-w*H+h*w
print(ans)


H, W = map(int, input().split())
h, w = map(int, input().split())
ans = (H-h) * (W-w)
print(ans)

a,b=map(int,input().split())
c,d=map(int,input().split())
print((a-c)*(b-d))

H,W = map(int,input().split())
h,w = map(int, input().split())
print(H *W-((h*W)+(w*H)-(h*w)))

a, b = list(map(int, input().split()))
a_l, b_l = list(map(int, input().split()))

print(((a - a_l) * (b - b_l)))


H, W = map(int, input().split())
h, w = map(int, input().split())
print((H-h)*(W-w))

H, W = list(map(int, input().split()))
h, w = list(map(int, input().split()))
a = H - h
b = W - w
print((a * b))


h1, w1 = list(map(int, input().split()))
h2, w2 = list(map(int, input().split()))

print(((h1 - h2) * (w1 - w2)))


h,w = list(map(int,input().split()))
i,j = list(map(int,input().split()))
print(((h-i)*(w-j)))


H, W = map(int, input().split())
h, w = map(int, input().split())
print((H - h) * (W - w))

H,M=map(int,input().split())
h,m=map(int,input().split())
print((H-h)*(M-m))

H, W = map(int, input().split())
h, w = map(int, input().split())

print((H-h) * (W-w))

H,W=list(map(int,input().split()))
h,w=list(map(int,input().split()))
print(((H-h)*(W-w)))


H, W = list(map(int, input().split()))
h, w = list(map(int, input().split()))
print(((H-h)*(W-w)))


H, W = map(int, input().split())
h, w = map(int, input().split())
print((W-w)*(H-h))