Problem:
 Score: 100 points    Problem Statement We have two distinct integers A and B .  Print the integer K such that |A - K| = |B - K| .  If such an integer does not exist, print IMPOSSIBLE instead.      Constraints  All values in input are integers.  0 \leq A,\ B \leq 10^9  A and B are distinct.         Input Input is given from Standard Input in the following format:  A  B       Output Print the integer K satisfying the condition.  If such an integer does not exist, print IMPOSSIBLE instead.        Sample Input 1 2 16      Sample Output 1 9  |2 - 9| = 7 and |16 - 9| = 7 , so 9 satisfies the condition.       Sample Input 2 0 3      Sample Output 2 IMPOSSIBLE  No integer satisfies the condition.       Sample Input 3 998244353 99824435      Sample Output 3 549034394

Solution (Python):
















































global FLAG_LOG
FLAG_LOG = False


def log(value):
    
    
    if FLAG_LOG:
        print(str(value))


def calculation(lines):
    
    
    A, B = list(map(int, lines[0].split()))
    
    
    
    
    
    
    
    

    ab = A+B
    if ab % 2 == 0:
        result = int(ab/2)
    else:
        result = 'IMPOSSIBLE'

    return [result]



def get_input_lines(lines_count):
    lines = list()
    for _ in range(lines_count):
        lines.append(input())
    return lines



def get_testdata(pattern):
    if pattern == 1:
        lines_input = ['2 16']
        lines_export = [9]
    if pattern == 2:
        lines_input = ['0 3']
        lines_export = ['IMPOSSIBLE']
    if pattern == 3:
        lines_input = ['998244353 99824435']
        lines_export = [549034394]
    return lines_input, lines_export



def get_mode():
    import sys
    args = sys.argv
    global FLAG_LOG
    if len(args) == 1:
        mode = 0
        FLAG_LOG = False
    else:
        mode = int(args[1])
        FLAG_LOG = True
    return mode



def main():
    import time
    started = time.time()
    mode = get_mode()
    if mode == 0:
        lines_input = get_input_lines(1)
    else:
        lines_input, lines_export = get_testdata(mode)

    lines_result = calculation(lines_input)

    for line_result in lines_result:
        print(line_result)

    
    
    
    
    
    
    
    
    
    
    



if __name__ == '__main__':
    main()

Solution (Python):
A,B=map(int,input().split())
if A==B:
  print(0)
else:
  if (A+B)%2==0:
    print((A+B)//2)
  else:
    print("IMPOSSIBLE")

Solution (Python):
a,b=map(int,input().split())
if (a+b)%2==0:
    print((a+b)//2)
else:
    print("IMPOSSIBLE")

Solution (Python):
A, B = map(int, input().split())
if (A+B) % 2 == 0:
    print((A+B)//2)
else:
    print("IMPOSSIBLE")

Solution (Python):
A,B=map(int,input().split())
if (A+B) % 2 == 1:print("IMPOSSIBLE")
else:print((A+B)//2)

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

k = a + b

if k % 2 == 0:
    print(int(k / 2))

else:
    print('IMPOSSIBLE')

Solution (Python):
a,b = map(int,input().split())
if (b-a)%2==0:
  print(int((b+a)/2))
else:
  print('IMPOSSIBLE')

Solution (Python):
a, b = map(int,input().split())
if (a+b)%2 == 0:
  print((a+b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
a, b = map(int, input().split())
print('IMPOSSIBLE' if (b + a) % 2 else (b + a) // 2)

Solution (Python):
a, b = map(int, input().split())
print('IMPOSSIBLE' if (b - a) % 2 else (b + a) // 2)

Solution (Python):
A, B = map(int, input().split())
A, B = sorted([A, B])
K = (B + A) / 2
if A <= K <= B and int(K) == K:
    print(int(K))
else:
    print('IMPOSSIBLE')

Solution (Python):
A, B = map(int, input().split())
if (A+B)%2 == 0:
  print ((A+B)//2)
else:
  print('IMPOSSIBLE')

Solution (Python):
a,b = map(int,input().split())
n=a+b
if n%2==0:print(int(n/2))
else:print("IMPOSSIBLE")

Solution (Python):
A,B=map(int,input().split())
if (A+B)/2==int((A+B)/2):
    print(int((A+B)/2))
else:
    print("IMPOSSIBLE")

Solution (Python):
a,b=map(int,input().split())
if abs(a-b)%2==1:
  print('IMPOSSIBLE')
else:
  print(min(a,b) + abs(a-b)//2)

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

print('IMPOSSIBLE' if (a-b)%2 > 0 else (a+b)//2)

Solution (Python):
A,B=map(int,input().split())
K=(A+B)/2
if(K.is_integer()==True):
  print(int(K))
else:
  print("IMPOSSIBLE")

Solution (Python):
A,B=map(int,input().split())
print((A+B)//2 if (A+B)%2==0 else "IMPOSSIBLE")

Solution (Python):
import sys
import math

def input():
    return sys.stdin.readline().rstrip()


def main():
    A,B=map(int,input().split())
    
    if (A + B) %2 ==0:
        print(int(A/2+B/2))
    else:
        print("IMPOSSIBLE")
    



if __name__ == "__main__":
    main()

Solution (Python):
n=input().split()
A=int(n[0])
B=int(n[1])
K=int((A+B)/2)
if abs(A-K)==abs(B-K):
    print(K)
else:
    print("IMPOSSIBLE")

Solution (Python):
a,b = map(int,input().split())
if (a+b)%2==0:
  print((a+b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):

import sys
A,B = map(int,input().split())

if not ( 0 <= A <= 10**9 and 0 <= B <= 10**9 ): sys.exit()

if A % 2 != B % 2:
    print('IMPOSSIBLE')
    sys.exit()
else:
    print(int((A+B)/2))

Solution (Python):
a, b = map(int, input().split())
n = a+b
if n % 2 == 0:
    print(n//2)
else:
    print('IMPOSSIBLE')

Solution (Python):
a, b = map(int,input().split())
x = a + b
if x % 2 == 0:
    print(x // 2)
else:
    print('IMPOSSIBLE')

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

s = a+b

if s%2 == 0:
    print(int(s/2))
else:
    print('IMPOSSIBLE')

Solution (Python):
import sys

[A, B] = [int(x) for x in sys.stdin.readline().split(" ")]
sum = A + B
if sum % 2 == 0:
    print(int(sum / 2))
else:
    print("IMPOSSIBLE")

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

K = (A+B) / 2
if (A-K) * (B-K) < 0 and K == int(K):
    print(int(K))
else:
    print('IMPOSSIBLE')

Solution (Python):
a, b = map(int, input().split())
if (a+b) % 2 == 0:
    print((a+b)//2)
else:
    print('IMPOSSIBLE')

Solution (Python):
a,b=map(int,input().split())
res = 0
c = a+b
if c % 2 == 1:
  print("IMPOSSIBLE")
else:
  res = int(c/2)
  print(res)

Solution (Python):
A, B = map(int, input().split())
if abs(A - B) % 2 == 1:
    print('IMPOSSIBLE')
else:
    print(int((A + B) / 2))

Solution (Python):
a, b = map(int, input().split())
print((a + b) // 2 if (a + b) % 2 == 0 else "IMPOSSIBLE")

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

print((A + B) // 2 if ((A + B) % 2 == 0) else "IMPOSSIBLE")

Solution (Python):
a,b = map(int,input().split())
k = a+b
if k%2:
    print('IMPOSSIBLE')
else:
    print(k//2)

Solution (Python):
def main():
 a,b = map(int,input().split())
 if abs(a + b) % 2 == 0:
     print(abs(a + b) // 2)
 else:
     print('IMPOSSIBLE')
main()

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

if ( A + B )%2 == 0:
    print((A + B)//2)
else:
    print('IMPOSSIBLE')

Solution (Python):
a,b=map(int,input().split())
c=b-a
if c%2==1:
  print("IMPOSSIBLE")
else:
  print(a+int(c/2))

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

if (A - B) % 2 == 0:
  print((A+B)//2)
else:
  print('IMPOSSIBLE')

Solution (Python):
a,b=map(int,input().split())
if (a-b)%2==1:
  print('IMPOSSIBLE')
else:
  print(min(a,b)+abs(a-b)//2)

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

if (a - b) % 2 == 0:
    print((a + b) // 2)
else:
    print('IMPOSSIBLE')

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

temp = A+B
if temp%2!=0:
  print("IMPOSSIBLE")
else:
  print(temp//2)

Solution (Python):
a,b = map(int, input().split())
if((a+b)%2==0):
  print(int((a+b)/2))
else:
  print("IMPOSSIBLE")

Solution (Python):
a, x =map(int, input().split())
if (a+x)%2 ==0:
  print(int((a+x)/2))
else:
  print('IMPOSSIBLE')

Solution (Python):
a,b = map(int,input().split())
if abs(a-b)%2==0:
  print(max(a,b)-abs(a-b)//2)
else:
  print('IMPOSSIBLE')

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

c = ((a**2) - (b**2)) 
d = 2*(a-b)
e = c/d

if int(e) == e:
    print(int(e))
else:
    print("IMPOSSIBLE")

Solution (Python):
a,b = map(int, input().split())
k = (a + b) // 2
if abs(a - k) == abs(b - k):
    print(round(k))
else:
    print("IMPOSSIBLE")

Solution (Python):
A, B = map(int, input().split())
print(int((A+B)/2) if (A+B)%2 == 0 else'IMPOSSIBLE')

Solution (Python):





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

c=a+b

if c%2==1:
  print("IMPOSSIBLE")
else:
  print(c//2)

Solution (Python):
a,b=map(int,input().split())
c=int((a+b)/2)
if (a+b)%2!=0:
  print("IMPOSSIBLE")
else:
  print(c)

Solution (Python):
A,B=map(int,input().split())
if (A+B)%2==0:
    print((A+B)//2)
else:
    print('IMPOSSIBLE')

Solution (Python):
a,b = map(int,input().split())
print(int((a+b)/2) if (a+b)%2 == 0 else'IMPOSSIBLE')

Solution (Python):
a,b = map(int,input().split())
if (a + b) % 2 == 0:
  print((a+b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
import sys, math
from collections import defaultdict
input = sys.stdin.readline
rs = lambda: input().strip()
ri = lambda: int(input())
rl = lambda: list(map(int, input().split()))
mod = 1000000007
sys.setrecursionlimit(1000000)

A, B = rl()

if (A+B) % 2 == 1:
	print('IMPOSSIBLE')
else:
	print((A+B)//2)

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

if (a+b)%2 == 0:
  print(int((a+b)/2))
else:
  print("IMPOSSIBLE")

Solution (Python):
a, b = map(int, input().split())
if (a+b) % 2 == 0:
  print((a + b) // 2)
else:
  print("IMPOSSIBLE")

Solution (Python):
A, B = map(int,input().split())
if (A+B)%2 == 0:
  print( (A+B)//2 )
else:
  print("IMPOSSIBLE")

Solution (Python):
A, B = [int(i) for i in input().split()]
if (A + B) / 2 == (A + B) // 2:
    print((A + B) // 2)
else:
    print("IMPOSSIBLE")

Solution (Python):
A,B = map(int, input().split())
if (A+B)%2==0:
  print((A+B)//2)
else:
  print('IMPOSSIBLE')

Solution (Python):
def resolve():
    A, B = list(map(int, input().split()))
    print((A+B)//2 if (A+B)%2==0 else "IMPOSSIBLE")

    
if '__main__' == __name__:
    resolve()

Solution (Python):
import sys
input = sys.stdin.readline

A,B = list(map(int,input().split()))
print('IMPOSSIBLE' if (A+B)/2 != int((A+B)/2) else (A+B)//2)

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

if (a+b) % 2 == 0:
    print(int((a+b)/2))
else:
    print("IMPOSSIBLE")

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

flg = False
if (b - a) % 2 == 0:
    flg = True

print((a+b)//2) if flg else print('IMPOSSIBLE')

Solution (Python):
x,y=map(int,input().split())
if (x+y)%2:
  print("IMPOSSIBLE")
else:
  print((x+y)//2)

Solution (Python):
A, B = map(int, input().split())
ans = "IMPOSSIBLE"
if (A+B)%2 == 0:
    ans = int((A+B)/2)
print(ans)

Solution (Python):
import sys
import math
import itertools
import bisect
from copy import copy
from collections import deque,Counter
from decimal import Decimal
def s(): return input()
def k(): return int(input())
def S(): return input().split()
def I(): return map(int,input().split())
def X(): return list(input())
def L(): return list(input().split())
def l(): return list(map(int,input().split()))
def lcm(a,b): return a*b//math.gcd(a,b)
def gcd(*numbers): reduce(math.gcd, numbers)
sys.setrecursionlimit(10 ** 9)
mod = 10**9+7
count = 0
ans = 0

a,b = I()
sa = abs(a-b)
if sa % 2 == 0:
    print((a+b)//2)
else:
    print("IMPOSSIBLE")

Solution (Python):



a, b = map(int, input().split())
print(a+(b-a)//2 if not (b-a)&1 else "IMPOSSIBLE")

Solution (Python):
a, b = map(int, input().split())
if abs(a - b) % 2 == 1:
    print('IMPOSSIBLE')
else:
    dif = abs(a - b) // 2
    if a < b:
        print(a + dif)
    else:
        print(b + dif)

Solution (Python):


import sys
stdin = sys.stdin

def ns(): return stdin.readline().rstrip()
def ni(): return int(ns())
def na(): return list(map(int, stdin.readline().split()))

def main():
    a, b = na()
    if a > b:
        a, b = b, a
    if (b - a) % 2 != 0:
        print("IMPOSSIBLE")
        quit()
    else:
        print(a + (b-a)//2)
if __name__ == "__main__":
    main()

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

if (a+b)%2==0:
  print((a+b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
import sys
import math
import itertools
import collections
import heapq
import re
import numpy as np

rr = lambda: sys.stdin.readline().rstrip()
rs = lambda: sys.stdin.buffer.readline().split()
ri = lambda: int(sys.stdin.readline())
rm = lambda: map(int, sys.stdin.buffer.readline().split())
rl = lambda: list(map(int, sys.stdin.readline().split()))
inf = float('inf')
mod = 10**9 + 7

a, b = rm()
if a & 1 == b & 1:
  print((a+b)//2)
else:
  print('IMPOSSIBLE')

Solution (Python):
def main():
    a,b=map(int,input().split(' '))
    if(abs(a+b)%2 !=0):
        print("IMPOSSIBLE")
    else:
        print(int((a+b)/2))

main()

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


if (A+B)%2==0:
	print((A+B)//2)
else:
	print("IMPOSSIBLE")

Solution (Python):


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

if (a + b)%2==0:
  print(int((a + b)/2))
else:
  print("IMPOSSIBLE")

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

c = A + B

K = c // 2



if (c % 2) != 0 :
    print("IMPOSSIBLE")

else:
    print(K)

Solution (Python):
A,B = map(int,input().split())
print((A+B)//2 if (A+B)%2==0 else "IMPOSSIBLE")

Solution (Python):
A,B = map(int, input().split())
if (A+B)%2 == 1:
  print('IMPOSSIBLE')
else:
  print((A+B)//2)

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

if (A+B) % 2 == 0:
  print(int((A+B)/2))
else:
  print('IMPOSSIBLE')

Solution (Python):
A, B = map(int, input().split())
 
 
K = (A + B) / 2
 
if (A + B) % 2 == 0:
    print(int(K))
 
else:
    print('IMPOSSIBLE')

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

if (a + b) % 2 == 0:
    print(int((a + b) / 2))
else:
    print('IMPOSSIBLE')

Solution (Python):
a, b = map(int, input().split())
if ((a+b)%2) == 0:
    c = (a+b)/2
    print(int(c))
else:
    print("IMPOSSIBLE")

Solution (Python):
a,b = map(int,input().split())
if a == b:
    print(0)
if int((a+b)/2) == (a+b)/2:
    print(int((a+b)/2))
else:
    print('IMPOSSIBLE')

Solution (Python):
import sys
input = lambda: sys.stdin.readline().rstrip()

def main():
    a, b = map(int, input().split())
    if (a - b) % 2 == 0:
        print(abs(a - b) // 2 + min(a, b))
    else:
        print('IMPOSSIBLE')

if __name__ == '__main__':
    main()

Solution (Python):
A, B = map(int,input().split())
if (A+B) % 2 == 0:
    print((A+B)//2)
else:
    print('IMPOSSIBLE')

Solution (Python):
a, b = map(int,input().split())
if (a - b) % 2 == 0:
  print(a-(a-b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
a,b = map(int,input().split())
k = (a+b)//2
if k-a==b-k:
  print(k)
else:
  print("IMPOSSIBLE")

Solution (Python):
A, B = map(int, input().split())
ans = A + B

if ans % 2 == 0:
  ans = int(ans//2)
  print(ans)
else:
  print('IMPOSSIBLE')

Solution (Python):
a,b=map(int, input().split())
if (a+b)%2==0:
  print((a+b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
A,B=map(int,input().split())
if (A+B)%2!=0: 
  print("IMPOSSIBLE")
else:
  print((A+B)//2)

Solution (Python):
a, b = map(int, input().split())
s = a + b
if s % 2 == 0:
    print(s//2)
else:
    print("IMPOSSIBLE")

Solution (Python):
import sys

A, B = map(int, sys.stdin.readline().split())
if abs(A - B) % 2 == 0:
    print((A + B) // 2)
else:
    print("IMPOSSIBLE")

Solution (Python):
A,B = (int(x) for x in input().split())
if (A+B)%2==0:
    print((A+B)//2)
else:
    print('IMPOSSIBLE')

Solution (Python):

c = eval(input().replace(" ", "+"))
print(c // 2 * (c % 2 < 1) or "IMPOSSIBLE")

Solution (Python):
a,b = [int(a) for a in input().split()]
k = (a+b)/2
if k==int(k):
  print(int(k))
else:
  print("IMPOSSIBLE")

Solution (Python):
a,b=map(int,input().split())
print((a+b)//2 if (a+b)%2==0 else "IMPOSSIBLE")

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

if (a+b)%2 == 0:
  print((a+b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
a=eval(input().replace(*' +'))
print(a%2*'IMPOSSIBLE'or a//2)

Solution (Python):
a=eval(input().replace(*' +'))
print(a%2*'IMPOSSIBLE'or a//2)

Solution (Python):
a,b=map(int,input().split())
if(abs(b-a)%2==0):
    print(abs(b-a)//2+min(a,b))
else:
    print('IMPOSSIBLE')

Solution (Python):
A,B = map(int,input().split())
if(abs(B-A)%2==0):
    print(abs(B-A)//2+min(A,B))
else:
    print('IMPOSSIBLE')

Solution (Python):


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

if (a + b) % 2 == 0:
    print(int((a + b) / 2))
else:
    print('IMPOSSIBLE')

Solution (Python):
a,b = map(int, input().split())
print(int((a+b)/2)) if (a+b)%2 == 0 else print("IMPOSSIBLE")

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

ans = ''
if a % 2 != b % 2:
    ans = 'IMPOSSIBLE'
else:
    ans = (a + b) // 2
print(ans)

Solution (Python):
a, b = map(int, input().split())
x = a+b
if x%2 == 0:
    print(x//2)
else:
    print('IMPOSSIBLE')

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

if (a+b)%2==0:
  print((a+b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
a,b=map(int,input().split())
if (b-a) % 2 == 1:
    print("IMPOSSIBLE")
else:
    print((a+b)//2)

Solution (Python):
a,b=map(int,input().split())
half=(a+b)/2
if half.is_integer():
  print(int(half))
else:
  print("IMPOSSIBLE")

Solution (Python):
a,b =map(int,input().split())
if  (a + b) % 2 == 0:
    print((a + b) // 2)
else:
    print("IMPOSSIBLE")

Solution (Python):
A,B = map(int, input().split())
if (A + B) % 2 == 0 :
  print ((A + B) // 2)
else :
  print ("IMPOSSIBLE")

Solution (Python):
A,B = map(int, input().split())
if (A + B) % 2 == 0 :
  print ((A + B) // 2)
else :
  print ("IMPOSSIBLE")

Solution (Python):
a, b = [int(i) for i in input("").split(" ")]
if a%2 != b%2:
  print('IMPOSSIBLE')
else:
  print(int((a+b)/2))

Solution (Python):
a,b = map(int,input().split())
if (a+b)%2==0:
    print((a+b)//2)
else:
    print("IMPOSSIBLE")

Solution (Python):
A,B = map(int, input().split())
if (A + B) % 2 == 0 :
  print ((A + B) // 2)
else :
  print ("IMPOSSIBLE")

Solution (Python):
a, b = map(int, input().split())
if (b - a) % 2 == 0:
  print(int(min([a, b]) + (max([a, b]) - min([a, b])) / 2))
else:
  print('IMPOSSIBLE')

Solution (Python):
a, b = map(int, input().split())
print((a+b)//2 if (a+b) % 2 == 0 else "IMPOSSIBLE")

Solution (Python):
a, b = map(int, input().split())
if (a + b) % 2 == 0 :
  print ((a + b) // 2)
else :
  print ("IMPOSSIBLE")

Solution (Python):
import math

def main():
    a, b = map(int, input().split())
    if ((a % 2) == 0 and (b % 2) == 0) or ((a % 2) == 1 and (b % 2) == 1):
        print(math.floor((a+b)/2))
    else:
        print('IMPOSSIBLE')
main()

Solution (Python):
a,b = map(int,input().split())
if (a + b) % 2 == 1: 
    print('IMPOSSIBLE')
    exit()
print((a+b) // 2)

Solution (Python):
arr = list(map(int, input().split()))

a, b = arr[0], arr[1]

if (a+b)%2 == 0: print(int((a+b)/2))
else: print("IMPOSSIBLE")

Solution (Python):
A,B=map(int,input().split())
K=abs((A+B)/2)
if K.is_integer()==True:
    print(int(K))
else:
    print('IMPOSSIBLE')

Solution (Python):
A, B = map(int, input().split())
K = (A+B)/2
if K.is_integer():
    print(int(K))
else:
    print("IMPOSSIBLE")

Solution (Python):
A, B = map(int, input().split())
print((A+B)//2 if (A+B) % 2 == 0 else "IMPOSSIBLE")

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

if (a + b) % 2 == 0:
    print((a + b)//2)
else:
    print('IMPOSSIBLE')

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

if (A+B)%2==0:
  print((A+B)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
a,b = (int(x) for x in input().split())

if (a + b) % 2 == 0:
    print((a+b)//2)

else:
    print("IMPOSSIBLE")

Solution (Python):
import sys

read = sys.stdin.read
readline = sys.stdin.readline
readlines = sys.stdin.readlines
sys.setrecursionlimit(10 ** 9)
INF = 1 << 60
MOD = 1000000007


def main():
    A, B = map(int, readline().split())
    if (A + B) % 2:
        print('IMPOSSIBLE')
    else:
        print((A + B) // 2)

    return


if __name__ == '__main__':
    main()

Solution (Python):
a,b=map(int,input().split())
if (a+b)%2==0:
  print((a+b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
inp1,inp2=map(int, input().split())
value=inp1+inp2
if value%2==0:
    print(int(value/2))
else:
    print("IMPOSSIBLE")

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

if (a+b)%2 == 0:
  print(int((a+b)/2))
else:
  print("IMPOSSIBLE")

Solution (Python):
a, b = map(int, input().split())
print((a + b) // 2 if (a + b) % 2 == 0 else 'IMPOSSIBLE')

Solution (Python):


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

if a != b:
    if (a + b) % 2 == 0:
        k = (a + b) // 2
        print(k)
    else:
        print("IMPOSSIBLE")
else:
    print(0)

Solution (Python):
a,b = map(int, input().split())
x = a +b
print(int(x/2) if x%2 == 0 else "IMPOSSIBLE")

Solution (Python):
import sys
a=sys.stdin.readline()
res=[i for i in a.split()]
r1,r2=float(res[0]),float(res[1])
v1,v2=r1.is_integer(),r2.is_integer()
if v1==v2==True:
    A,B=int(r1),int(r2)
    if 0<=(A and B)<=1000000000:
        w=(A+B)/2
        v3=w.is_integer()
        if v3==True:
            print(int(w))
        elif v3!=True:
            print("IMPOSSIBLE")

Solution (Python):
a,b=map(int,input().split())
if abs(a-b)%2:
  print('IMPOSSIBLE')
else:
  print((a+b)//2)

Solution (Python):
x,y = [int(a) for a in input().split()]

if ((x+y)%2 == 1):
      print("Impossible".upper())
else:
      print((x+y)//2)

Solution (Python):







a = list(map(int, input().split()))
if ((a[0] + a[1]) // 2) * 2 != a[0] + a[1]:
    print("IMPOSSIBLE")
else:
    print(((a[0] + a[1]) // 2))

Solution (Python):
a,b = map(int,input().split())
if (a+b) % 2 == 0:
    print((a+b)//2)
else:
    print("IMPOSSIBLE")

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

if (A+B)%2 == 0:
  print(int((A+B)/2))
else:
  print("IMPOSSIBLE")

Solution (Python):
A, B = map(int, input().split())
print((A+B)//2 if (A+B)%2 == 0 else "IMPOSSIBLE")

Solution (Python):
print((lambda x:('IMPOSSIBLE' if (x[0]+x[1])%2==1 else (x[0]+x[1])//2))(list(map(int,input().split()))))

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

if (A + B) % 2 == 0:
    print(int((A+B)/2))
else:
    print("IMPOSSIBLE")

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

k = (a + b) // 2

if abs(a-k) == abs(b-k):
  print(int(k))
else :
  print("IMPOSSIBLE")

Solution (Python):
def solve():
    a, b = map(int, input().split())
    n = a + b
    if n % 2 == 0:
        print((a+b)//2)
    else:
        print('IMPOSSIBLE')


if __name__ == '__main__':
    solve()

Solution (Python):
A,B = map(int, input().split())
if (A+B)%2 == 0:
  print((A+B)//2)
else:
  print('IMPOSSIBLE')

Solution (Python):
A,B = map(int,input().split())
 
if (A+B)%2==0:
  print((A+B)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
a,b = map(int,input().split())
if (a+b) % 2 == 0:
  print(int((a+b)/2))
else:
  print("IMPOSSIBLE")

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

if (A+B)%2==0:
  print((A+B)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
a,b=map(int,input().split())
if abs(a-b)%2==1:
    print("IMPOSSIBLE")
else:
    print(int((a+b)/2))

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

if ((A+B)/2)%1==0.0:
    print(int((A+B)/2))
else:
    print("IMPOSSIBLE")

Solution (Python):
a,b = map(int,input().split())
print((a+b)//2 if (a+b)%2 == 0 else "IMPOSSIBLE")

Solution (Python):
a, b = map(int, input().split())
if (a+b) % 2 != 0:
    print('IMPOSSIBLE')
else:
    print((a+b)//2)

Solution (Python):
a, b = map(int, input().split())
if (a+b) % 2 != 0:
    print('IMPOSSIBLE')
else:
    print((a+b)//2)

Solution (Python):
A,B=map(int,input().split())
if abs(A-B)%2==0:
  print((A+B)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
n,k = map(int,input().split())

if (n+k)%2==0:
    print((n+k)//2)
else:
    print('IMPOSSIBLE')

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

answer = 'IMPOSSIBLE'
start = (A + B) // 2 - 1
end = (A + B) // 2 + 1


for i in range(start, end+1):
    a = abs(A - i)
    b = abs(B - i)
    
    if a == b:
        answer = i
        break

print(answer)

Solution (Python):
a,b=map(int,input().split())
if (a+b)%2==1:
  print('IMPOSSIBLE')
else:
  print((a+b)//2)

Solution (Python):
A,B = [ int(i) for i in input().split() ]

print(int((A+B)//2) if (A+B)%2 == 0 else "IMPOSSIBLE")

Solution (Python):
def main():
    a, b = map(int, input().split())
    n = b - a
    if n % 2 ==0:
        ans = a + int(n/2)
        print(ans)
    else:
        print('IMPOSSIBLE')

if __name__ == '__main__':
    main()

Solution (Python):
def solve():
	a, b = map(int, input().split())
	if (a + b) % 2 == 1:
		return "IMPOSSIBLE"
	else:
		return int((a + b) / 2)
		
		
if __name__ == "__main__":
	print(solve())

Solution (Python):
a, b = map(int, input().split())
if abs(a-b) % 2 != 0:
    print("IMPOSSIBLE")
else:
    print(min(a,b) + abs(a-b) // 2)

Solution (Python):
A, B = map(int, input().split())
if (A + B) % 2 == 0:
    print((A + B) // 2)
else:
    print("IMPOSSIBLE")

Solution (Python):
a , b = map(int,input().split())
if (a + b) % 2 == 0:
  print(abs(a + b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
a, b = map(int, input().split())
ans = (abs(a - b) // 2) + min(a, b)
print(ans if abs(a - b) % 2 == 0 else "IMPOSSIBLE")

Solution (Python):
a,b = map(int,input().split())
ans = a + b

if ans % 2 == 0:
    print(int(ans / 2))
else:
    print('IMPOSSIBLE')

Solution (Python):
import sys
sys.setrecursionlimit(10**6)

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

if (a-b)%2 == 0:
    print((a+b)//2)
else:
    print('IMPOSSIBLE')

Solution (Python):
a, b = map(int, input().split())
if (a + b) % 2 == 0:
    print((a + b) // 2)
else:
    print('IMPOSSIBLE')

Solution (Python):
a, b = map(int, input().split())
if (a + b) % 2 == 0:
    print((a + b) // 2)
else:
    print('IMPOSSIBLE')

Solution (Python):
a,b=map(int,input().split());print('IMPOSSIBLE' if (b-a)%2!=0 else int((a+b)/2))

Solution (Python):
A,B=map(int,input().split())
if (A+B)%2!=0:
  print("IMPOSSIBLE")
else:
  print((A+B)//2)

Solution (Python):
a,b=map(int,input().split())
if a%2==0 and b%2==0:
  print((a+b)//2)
  
elif a%2!=0 and b%2!=0:
  print((a+b)//2)
  
else:
  print('IMPOSSIBLE')

Solution (Python):
a,b = map(int,input().split())
print((a+b)//2 if (a+b)%2 == 0 else "IMPOSSIBLE")

Solution (Python):
A,B  = map(int,input().split())
print( (A + B) // 2 if (A + B) % 2 == 0 else 'IMPOSSIBLE' )

Solution (Python):
a,b=map(int,input().split())
print((a+b)//2 if (a+b)%2==0 else "IMPOSSIBLE")

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

if((a+b)%2 == 0):
    print((a+b)//2)
else:
    print("IMPOSSIBLE")

Solution (Python):
a,b=map(int,input().split())
ans=0
if (a-b)%2!=0:
    ans="IMPOSSIBLE"
else:
    ans=int((a+b)/2)
print(ans)

Solution (Python):
a,b=map(int,input().split())
if (a+b)%2==0:
  print((a+b)//2)
else:
  print("IMPOSSIBLE")

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

print('IMPOSSIBLE' if (A + B) % 2 == 1 else (A + B) // 2)

Solution (Python):
a,b=map(int, input().split())
print((a+b)//2 if (a+b)%2==0 else "IMPOSSIBLE")

Solution (Python):
A,B = map(int,input().split())
if (A + B) % 2 == 0:
    print(int((A + B) / 2))
else:
    print("IMPOSSIBLE")

Solution (Python):
A, B = map(int, input().split())
if (A+B) % 2 == 0:
  print((A + B) // 2)
else:
  print("IMPOSSIBLE")

Solution (Python):
a,b = map(int,input().split())
k = (a+b) // 2
if (a+b)%2 != 0:
    print('IMPOSSIBLE')
    exit()
print(k)

Solution (Python):
a,b = map(int,input().split())
ans = [(a+b)//2,"IMPOSSIBLE"]
print(ans[(a+b)%2])

Solution (Python):
a, b = map(int, input().split())
print((a + b) // 2 if (a + b) % 2 == 0 else 'IMPOSSIBLE')

Solution (Python):
a, b = map(int, input().split())
print((a + b) // 2 if (a + b) % 2 == 0 else "IMPOSSIBLE")

Solution (Python):
import sys

input = lambda: sys.stdin.readline().rstrip()


def solve():
    A, B = map(int, input().split())

    if (A + B) % 2 == 0:
        ans = (A + B) // 2
    else:
        ans = 'IMPOSSIBLE'

    print(ans)


if __name__ == '__main__':
    solve()

Solution (Python):
a,b=map(int,input().split())
print('IMPOSSIBLE' if (a+b)%2!=0 else (a+b)//2)

Solution (Python):
a,b = map(int, input().split())
if (a+b) % 2 == 0:
    print((a+b)//2)
else:
    print('IMPOSSIBLE')

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

print((A+B)//2 if (A+B)%2==0 else "IMPOSSIBLE")

Solution (Python):
a,b=map(int,input().split())
print((a+b)//2 if (a+b)%2==0 else "IMPOSSIBLE")

Solution (Python):
a,b=map(int,input().split())
if (a+b)%2==0:
    print(int((a+b)/2))
else:
    print('IMPOSSIBLE')

Solution (Python):
a,b = map(int,input().split())
if (a + b) % 2 == 0:
    print((a + b) // 2)
else:
    print('IMPOSSIBLE')

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

if (A+B)%2==0:
  print(int((A+B)/2))
else:
  print('IMPOSSIBLE')

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



if a % 2 != b % 2:
	print('IMPOSSIBLE')
else:
  	print(int((a + b) / 2))

Solution (Python):
def inp():return map(int,input().split())
a,b=inp()
if (a+b)%2==0:print((a+b)//2)
else:print("IMPOSSIBLE")

Solution (Python):
a,b=map(int,input().split())
if (a+b)%2 == 0:
  print((a+b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
a, b = map(int,input().split())
if (a % 2 != b % 2):
    print("IMPOSSIBLE")
else:
    print(int((a + b) / 2))

Solution (Python):
a,b = list(map(int,input().split()))
print('IMPOSSIBLE' if a %2 != b %2 else (a+b)//2)

Solution (Python):
a,b=map(int,input().split())
if a%2==b%2:
    print((a+b)//2)
else:
    print("IMPOSSIBLE")

Solution (Python):
a,b = map(int,input().split())
if (a+b)/2 == (a+b)//2:
  print((a+b)//2)
else:
  print("IMPOSSIBLE")

Solution (Python):
a,b = map(int, raw_input().split(' '))
if a > b:b,a = a,b
if (b - a) % 2 == 0: print a + (b-a)/2
else: print 'IMPOSSIBLE'

Solution (Python):
a,b = map(int, input().split())
if (a+b) % 2 == 0:
  ans = int((a+b) / 2)
  print(ans)
else:
  print('IMPOSSIBLE')

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

k = (a+b)/2

if abs(a-k) == abs(b-k) and (a+b) % 2 == 0:
    print(int(k))
else:
    print("IMPOSSIBLE")

Solution (Python):
a, b = map(int, input().split())
print((a+b)//2 if (a+b)%2 == 0 else 'IMPOSSIBLE')

Solution (Python):
from sys import stdin, setrecursionlimit


def main():
    input = stdin.buffer.readline
    a, b = map(int, input().split())
    if (a + b) % 2 == 0:
        print((a + b) // 2)
    else:
        print('IMPOSSIBLE')


if __name__ == "__main__":
    setrecursionlimit(10000)
    main()

Solution (Python):
import sys


def input():
    return sys.stdin.readline().strip()

def main():
    a, b = map(int, input().split())
    if abs(a-b) % 2 != 0:
        print("IMPOSSIBLE")
        return
    if a >= b:
        print((a-b)//2+b)
        return
    print((b-a)//2+a)
    
main()

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

if (A + B) % 2 == 0:
    print(int((A + B) / 2))
    
else:
    print("IMPOSSIBLE")

Solution (Python):
a, b = map(int, input().split())
if abs(a - b) % 2 == 0:
  print(min(a, b) + abs(a - b) // 2)
else:
  print('IMPOSSIBLE')

Solution (Python):
a , b = map(int,input().split())
x = (a+b) / 2
print(int(x) if x.is_integer() else 'IMPOSSIBLE' )

Solution (Python):
A, B = map(int, input().split(' '))
if (A + B) // 2 == (A + B) / 2:
  print((A + B) // 2)
else:
  print('IMPOSSIBLE')

Solution (Python):
def main():
    A, B = map(int, input().split())
    mi = min(A, B)
    ma = max(A, B)
    if (ma - mi) % 2 == 0:
        print((ma + mi) // 2)
    else:
        print("IMPOSSIBLE")


if __name__ == '__main__':
    main()

Solution (Python):
a , b = map(int,input().split())
x = (a+b) / 2
print(int(x) if x.is_integer() else 'IMPOSSIBLE' )

Solution (Python):
a,b=map(int,input().split())
if (a+b)%2==0:
    print((a+b)//2)
else:
    print('IMPOSSIBLE')

Solution (Python):
A, B = map(int,input().split())
K = (A+B) / 2
if K == int(K) :
    print(int(K))
else : print("IMPOSSIBLE")

Solution (Python):
a,b = map(int,input().split())
if (a+b)%2==0:
    print((a+b)//2)
else:
    print("IMPOSSIBLE")