Problem:
 Score : 100 points    Problem Statement 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 1 3 2
2 1      Sample Output 1 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.       Sample Input 2 5 5
2 3      Sample Output 2 6       Sample Input 3 2 4
2 4      Sample Output 3 0

Solution (Python):
a,b=map(int,input().split())
x,y=map(int,input().split())
print((a-x)*(b-y))

Solution (Python):

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

A = (H-h)*(W-w)

print(A)

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

Solution (Python):
import sys
input = sys.stdin.readline
H,W=map(int,input().split())
h,w=map(int,input().split())

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

Solution (Python):
h, w = map(int,input().split())
h1, w1 = map(int,input().split())
print((h-h1)*(w-w1))

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

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

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

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

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

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

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

Solution (Python):

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

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

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

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

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

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

Solution (Python):
H,W=(int(x) for x in input().split())
h,w=(int(x) for x in input().split())

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

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

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

Solution (Python):
"""
n = int(sys.stdin.readline())
a, b = map(int, sys.stdin.readline().split())
c = list(map(int, sys.stdin.readline().split()))
s = [list(map(int,list(sys.stdin.readline()))) for i in range(h)]  

a = 100
b = 0.987654321
print('{0:06d}-{1:6f}'.format(a,b))  
000100-0.987654


char_list = list("abcd") 
"""

import math
import sys
import itertools
import queue
from fractions import gcd

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


mod = 1000000007

if __name__ == "__main__":
    H, W = map(int, sys.stdin.readline().split())
    h, w = map(int, sys.stdin.readline().split())
    print(H * W - (h * W + w * H - h * w))

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

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

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

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

Solution (Python):
H, W = map(int, input().split())
h, w = map(int, input().split())
r = H*W - (h*W+(H-h)*w)

print(r)

Solution (Python):
N = input().split()
H = int(N[0])
W = int(N[1])

n = input().split()
h = int(n[0])
w = int(n[1])

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

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

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

Solution (Python):

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

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

Solution (Python):
A,B = list(map(int,input().split()))
a,b = list(map(int,input().split()))

print((A-a)*(B-b))

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

Solution (Python):



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







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

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

Solution (Python):
a,b = map(int, input().split())
c,d = map(int, input().split())

sel = a * b
d1 = b * c
d2 = (a - c) * d

result = sel -d1 -d2
print( result )

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

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

Solution (Python):

def get_numbers():
    return map(int, input().split())

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

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

Solution (Python):


H, W = [int(x) for x in input().split()]
h, w = [int(x) for x in input().split()]
print((H-h)*(W-w))

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

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

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

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

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

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

Solution (Python):
import numpy as np
H,W = map(int, input().split())
h,w = map(int, input().split())
matrix = [[1 if (i>w-1 and j>h-1) else 0 for i in range(W)] for j in range(H)]
print(np.sum(matrix))

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

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

Solution (Python):
w, h = map(int, input().split())

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

ans = (w-a) * (h-b)

print(ans)

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

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

Solution (Python):

H, W = (int(_) for _ in input().split())
h, w =  (int(_) for _ in input().split())
total = H*W
remaining = total - (h*W + w*H - h*w)
print(remaining)

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

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

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

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


black = h * W + H * w - h * w 
white = H * W - black
print(white)

Solution (Python):
str_in = input().split()
height = int(str_in[0])
width  = int(str_in[1])

str_in = input().split()
hcut = int(str_in[0])
wcut = int(str_in[1])

ans = (height - hcut) * (width - wcut)
print (ans)

Solution (Python):
H, W = map(int, input().split())
h_a, w_a = map(int, input().split())
print(H * W - (h_a * W + w_a * H) + h_a * w_a)

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

Solution (Python):
x,y = map(int,input().split())
a,b = map(int,input().split())
print(x*y-(a*y+b*x-a*b))

Solution (Python):
import numpy as np

H,W = map(int,input().split())
matrix = np.zeros((H,W))

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

for i in range(h):
  matrix[i,:] = 1
for i in range(w):
  matrix[:,i] = 1

print(int(H*W - np.sum(np.sum(matrix))))

Solution (Python):
I=lambda:map(int,input().split())
H,W=I()
h,w=I()
print((H-h)*(W-w))

Solution (Python):
H,W = map(int,input().split())

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

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

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

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

Solution (Python):
"""


 = sys.stdin.readline().rstrip()
 = list(sys.stdin.readline().rstrip())


 = int(sys.stdin.readline())
 = map(int, sys.stdin.readline().split())
 = list(map(int, sys.stdin.readline().split()))
 = [list(map(int,list(sys.stdin.readline().split()))) for i in range(h)]  


a = 100
b = 0.987654321
print("{0:06d}-{1:6f}".format(a,b))
000100-0.987654


char_list = list("abcd") 
"""

import math
import sys
import itertools
import queue
from fractions import gcd

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

mod = 1000000007

if __name__ == "__main__":
    H,W = map(int, sys.stdin.readline().split())
    h2, w2 = map(int, sys.stdin.readline().split())
    n=(H-h2) * (W-w2)
    print(n)

Solution (Python):
def main43():
    data1 = input().split()
    hw1 = []
    for i in range(2):
        hw1.append(int(data1[i]))
    data2 = input().split()
    hw2 = []
    for i in range(2):
        hw2.append(int(data2[i]))
    result = (hw1[0] - hw2[0]) * (hw1[1] - hw2[1])
    print(result)

if __name__ == "__main__":
    main43()

Solution (Python):
r,c=map(int,input().split())
r2,c2=map(int,input().split())

res=(r-r2)*(c-c2)

print(res)

Solution (Python):
a,s=map(int,input().split())
f,g=map(int,input().split())
print((a-f)*(s-g))

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

Solution (Python):
input1 = input().split(" ")
input2 = input().split(" ")
lh = int(input1[0])
lw = int(input1[1])
sh = int(input2[0])
sw = int(input2[1])

print((lh-sh)*(lw-sw))

Solution (Python):
HW = [int(i) for i in input().split()]
hw = [int(i) for i in input().split()]

H = HW[0]
W = HW[1]
h = hw[0]
w = hw[1]

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

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


result = H * W - h * W - w * H + h * w;

print(result);

Solution (Python):
h,w = map(int,input().split())
l,m = map(int,input().split())
print((h-l)*(w-m))

Solution (Python):

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

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

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

Solution (Python):
h, w = map(int, input().split())
n, m = map(int, input().split())


print(h*w - (n*w + m*h - n*m))

Solution (Python):
uh,uw = map(int, input().split())
h, w = map(int, input().split())
print((uh-h)*(uw-w))

Solution (Python):
H,W = (int(x) for x in input().split())
h,w = (int(x) for x in input().split())

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Solution (Python):
H, W = map(int, input().split())
h, w = map(int, input().split())
print(max(H-h, 0) * max(W-w, 0))

Solution (Python):
h,w = map(int,input().split())
a,b =map(int,input().split())
print(h * w -(h * b + w * a - a * b))

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

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

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

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

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

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

Solution (Python):



H, W = map(int, input().split())
A, B = map(int, input().split())


ans = (H * W) - (A * W + B * H - A * B)


print(ans)

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

A = H-h
B= W-w

print(A*B)

Solution (Python):
uh, uw = map(int, input().split())
h, w = map(int, input().split())
print(int((uh*uw) - (uh*w) - (uw*h) + (h*w)))

Solution (Python):
size = input().split()
fill = input().split()

print(int(size[0])*int(size[1])-int(fill[0])*int(size[1])-int(fill[1])*int(size[0])+int(fill[0])*int(fill[1]))

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

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

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

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

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

Solution (Python):
w,h = map(int, input().split())
w1,h1 = map(int, input().split())
ans = (w-w1)*(h-h1)
print(ans)

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

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

Solution (Python):

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

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

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

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

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

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

Solution (Python):
import numpy as np



"""
directly out
agc*
*agc_
indirectly

*gac
gac*
*acg
acg*
a*gc
ag*c

a =0
c =1
g = 2
t = 3
"""














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

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

Solution (Python):
def main():

    """ convenient functions
    
    
    
    
    
    """

    """convenient decorator
    
    
        
        
        
        
        
        
        
        
        
        
    """
    
    
    import sys
    sys.setrecursionlimit(10**7)
    from itertools import accumulate, combinations, permutations, product 
    
    from math import factorial, ceil, floor, sqrt
    def factorize(n):
        """return the factors of the Arg and count of each factor
        
        Args:
            n (long): number to be resolved into factors
        
        Returns:
            list of tuples: factorize(220) returns [(2, 2), (5, 1), (11, 1)]
        """
        fct = []  
        b, e = 2, 0  
        while b * b <= n:
            while n % b == 0:
                n = n // b
                e = e + 1
            if e > 0:
                fct.append((b, e))
            b, e = b + 1, 0
        if n > 1:
            fct.append((n, 1))
        return fct
    def combinations_count(n, r):
        """Return the number of selecting r pieces of items from n kinds of items.
        
        Args:
            n (long): number
            r (long): number
        
        Raises:
            Exception: not defined when n or r is negative
        
        Returns:
            long: number
        """
        
        if n < 0 or r < 0:
            raise Exception('combinations_count(n, r) not defined when n or r is negative')
        if n - r < r: r = n - r
        if r < 0: return 0
        if r == 0: return 1
        if r == 1: return n
        numerator = [n - r + k + 1 for k in range(r)]
        denominator = [k + 1 for k in range(r)]
        for p in range(2,r+1):
            pivot = denominator[p - 1]
            if pivot > 1:
                offset = (n - r) % p
                for k in range(p-1,r,p):
                    numerator[k - offset] /= pivot
                    denominator[k] /= pivot
        result = 1
        for k in range(r):
            if numerator[k] > 1:
                result *= int(numerator[k])
        return result
    def combinations_with_replacement_count(n, r):
        """Return the number of selecting r pieces of items from n kinds of items allowing individual elements to be repeated more than once.
        
        Args:
            n (long): number
            r (long): number
        
        Raises:
            Exception: not defined when n or r is negative
        
        Returns:
            long: number
        """
        if n < 0 or r < 0:
            raise Exception('combinations_with_replacement_count(n, r) not defined when n or r is negative')
        elif n == 0:
            return 1
        else:
            return combinations_count(n + r - 1, r)
    from bisect import bisect_left, bisect_right
    from collections import deque, Counter, defaultdict 
    from heapq import heapify, heappop, heappush, heappushpop, heapreplace,nlargest,nsmallest 
    from copy import deepcopy, copy 
    import operator
    from operator import itemgetter
    
    
    from functools import reduce, lru_cache
    def chmin(x, y):
        """change minimum
        if x > y, x = y and return (x, True).
        convenient when solving problems of dp[i]
        
        Args:
            x (long): current minimum value
            y (long): potential minimum value
        
        Returns:
            (x, bool): (x, True) when updated, else (x, False)
        """
        if x > y:
            x = y
            return (x, True)
        else:
            return (x, False)
    def chmax(x, y):
        """change maximum
        if x < y, x = y and return (x, True).
        convenient when solving problems of dp[i]
        
        Args:
            x (long): current maximum value
            y (long): potential maximum value
        
        Returns:
            (x, bool): (x, True) when updated, else (x, False)
        """
        if x < y:
            x = y
            return (x, True)
        else:
            return (x, False)

    from fractions import gcd 
    def gcds(numbers):
        return reduce(gcd, numbers)
    def lcm(x, y):
        return (x * y) // gcd(x, y)
    def lcms(numbers):
        return reduce(lcm, numbers, 1)

    
    
    INF = 10 ** 18
    MOD = 10 ** 9 + 7
    modpow = lambda a, n, p = MOD: pow(a, n, p) 
    def modinv(a, p = MOD):
        
        
        return modpow(a, p-2, p)
    def modinv_list(n, p = MOD):
        if n <= 1:
            return [0,1][:n+1]
        else:
            inv_t = [0,1]
            for i in range(2, n+1):
                inv_t += [inv_t[p % i] * (p - int(p / i)) % p]
            return inv_t
    def modfactorial_list(n, p = MOD):
        if n == 0:
            return [1]
        else:
            l = [0] * (n+1)
            tmp = 1
            for i in range(1, n+1):
                tmp = tmp * i % p
                l[i] = tmp
            return l
    def modcomb(n, k, fac_list = [], p = MOD):
        
        
        from math import factorial
        if n < 0 or k < 0 or n < k: return 0
        if n == 0 or k == 0: return 1
        if len(fac_list) <= n:
            a = factorial(n) % p
            b = factorial(k) % p
            c = factorial(n-k) % p
        else:
            a = fac_list[n]
            b = fac_list[k]
            c = fac_list[n-k]
        return (a * modpow(b, p-2, p) * modpow(c, p-2, p)) % p
    def modadd(a, b, p = MOD):
        return (a + b) % MOD
    def modsub(a, b, p = MOD):
        return (a - b) % p
    def modmul(a, b, p = MOD):
        return ((a % p) * (b % p)) % p
    def moddiv(a, b, p = MOD):
        return modmul(a, modpow(b, p-2, p))

    """ initialize variables and set inputs
    
        
        
    
        
        
        
        
        
    
        
        
        
        
    
        
        
    """

    
    r = lambda: sys.stdin.readline().strip()
    r_int = lambda: int(r())
    R = lambda: list(map(int, r().split()))
    Rmap = lambda: map(int, r().split())
    Rfloat = lambda: list(map(float, r().split()))
    Rtuple = lambda: tuple(map(int, r().split()))

    """ how to treat input
    
    
    
    
    
    
    
    """

    if __name__ != '__main__':
        
        sys.stdin = open('sample.txt')

    
    

    H, W = R()
    h, w = R()
    print(H * W - h * W - H * w + h * w)
    
    
    

    """memo: how to use defaultdict of list
    
    Dic = defaultdict(list)
    
    Dic[x].append(y)
    
    for k, v in Dic.items():
    """

if __name__ == '__main__':
    main()

Solution (Python):
H,W = map(int,input().split())

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

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

Solution (Python):
H, W = map(int,input().split())

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

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

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

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

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

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

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

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

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

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

Solution (Python):
high, width = map(int, input().split())
h, w = map(int, input().split())

ans = high*width - (h*width + w*high - w*h)

print(ans)

Solution (Python):

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

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

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

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

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

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

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

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

s = H * W 
b1 = h * W
b2 = w * (H - h)

print(s - b1 - b2)

Solution (Python):
H, W = map(int, input().split(' '))
h, w = map(int, input().split(' '))

s = H * W 
b1 = h * W
b2 = w * (H - h)

print(s - b1 - b2)

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


main()

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

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

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

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

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

Solution (Python):
a, b = map(int, raw_input().split())
c, d = map(int, raw_input().split())
x = a - c
y = b - d
print x * y

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

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

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

all = H*W
minus = h*W + w*H - h*w
print(all - minus)

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

Solution (Python):


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

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

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

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

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

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

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

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

Solution (Python):
h1, w1 = map(int,input().split())
h2, w2 = map(int,input().split())

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

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

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

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

Solution (Python):
a,b = list(map(int,input().split(" ")))
c,d = list(map(int,input().split(" ")))

print(a*b-(a*d+b*c-c*d))

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

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

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

Solution (Python):
W,H=map(int,input().split())
w,h=map(int,input().split())
S=W*H
black=W*h+H*w-w*h
print(S-black)

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

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

Solution (Python):



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

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

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

Solution (Python):
import numpy as np

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

mat = np.ones(shape=(H, W))
mat[:h, :] = 0
mat[:, :w] = 0
print(int(mat.sum()))

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


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

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

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

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

Solution (Python):
def main():
    H, W = map(int,input().split())
    h, w = map(int,input().split())

    point = W * H

    delete_h = h * W
    delete_w = w * H

    kaburi = h * w

    ans = point - (delete_h + delete_w - kaburi)
    print(ans)


if __name__ == '__main__':
    main()

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

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

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

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

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

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

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

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

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

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

Solution (Python):
h, w = list(map(int, input().split()))
a, b = list(map(int, input().split()))
print((h-a)*(w-b))

Solution (Python):
from sys import stdin

H, W = [int(x) for x in stdin.readline().rstrip().split()]
h, w = [int(x) for x in stdin.readline().rstrip().split()]

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

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

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

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

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

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

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

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

Solution (Python):
H,W = (int(x) for x in input().split())
eh,ew = (int(x) for x in input().split())
print(int(H-eh)*int(W-ew))

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

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

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

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

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

Solution (Python):
hw=list(map(int,input().split()))
xy=list(map(int,input().split()))
print((hw[0]-xy[0])*(hw[1]-xy[1]))

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

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

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

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

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

print(ans)

Solution (Python):


rac_H, rac_W = input().split()
rac_h, rac_w = input().split()

rac_all = (int(rac_H) - int(rac_h)) * (int(rac_W) - int(rac_w))
print(rac_all)

Solution (Python):
H,W = list(map(int,input().split()))
h,w = list(map(int,input().split()))
list = [[1]*W for i in range(0,H)]
for i in range(h):
    for j in range(W):
        list[i][j] = 0
for i in range(H):
    for j in range(w):
        list[i][j] = 0
result = sum(map(sum, list))
print(result)

Solution (Python):
n1, n2 = [int(i) for i in input().split()]
n3, n4 = [int(j) for j in input().split()]

r1 = (n1 * n2) - (n1 * n4) - (n2 * n3)  + (n4 * n3)

print(r1)

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

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

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

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

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

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

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

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

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

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

answer=(H-h)*(W-w)

print(answer)

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

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

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

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

print(H * W - black)

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

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

white = int(H * W)
black = int(H*w + W*h)
white = white - black + h*w

print(white)