Problem: We have N+M balls, each of which has an integer written on it.   It is known that:    * The numbers written on N of the balls are even.   * The numbers written on M of the balls are odd.  Find the number of ways to choose two of the N+M balls (disregarding order) so that the sum of the numbers written on them is even.   It can be shown that this count does not depend on the actual values written on the balls.

Submission attempts (in order):
import math
import string


def readints():
    return list(map(int, input().split()))


def nCr(n, r):
    return math.factorial(n)//(math.factorial(n-r)*math.factorial(r))


def has_duplicates2(seq):
    seen = []
    for item in seq:
        if not(item in seen):
            seen.append(item)
    return len(seq) != len(seen)


def divisor(n):
    divisor = []
    for i in range(1, n+1):
        if n % i == 0:
            divisor.append(i)
    return divisor


# coordinates
dx = [-1, -1, -1, 0, 0, 1, 1, 1]
dy = [-1, 0, 1, -1, 1, -1, 0, 1]


n, m = map(int, input().split())
#print(n, m)
if n == 1:
    print(0)
    exit()
a = nCr(n, 2)
print(a+m)


import math
import string


def readints():
    return list(map(int, input().split()))


def nCr(n, r):
    return math.factorial(n)//(math.factorial(n-r)*math.factorial(r))


def has_duplicates2(seq):
    seen = []
    for item in seq:
        if not(item in seen):
            seen.append(item)
    return len(seq) != len(seen)


def divisor(n):
    divisor = []
    for i in range(1, n+1):
        if n % i == 0:
            divisor.append(i)
    return divisor


# coordinates
dx = [-1, -1, -1, 0, 0, 1, 1, 1]
dy = [-1, 0, 1, -1, 1, -1, 0, 1]


n, m = map(int, input().split())
#print(n, m)
if n == 1:
    print(0)
    exit()
if n == 0:
    print(m)
    exit()
a = nCr(n, 2)
print(a+m)


import math
import string


def readints():
    return list(map(int, input().split()))


def nCr(n, r):
    return math.factorial(n)//(math.factorial(n-r)*math.factorial(r))


def has_duplicates2(seq):
    seen = []
    for item in seq:
        if not(item in seen):
            seen.append(item)
    return len(seq) != len(seen)


def divisor(n):
    divisor = []
    for i in range(1, n+1):
        if n % i == 0:
            divisor.append(i)
    return divisor


# coordinates
dx = [-1, -1, -1, 0, 0, 1, 1, 1]
dy = [-1, 0, 1, -1, 1, -1, 0, 1]


n, m = map(int, input().split())
#print(n, m)
if n == 1:
    print(math.floor(m/2))
    exit()
if n == 0:
    print(m)
    exit()
a = nCr(n, 2)
print(a+m)


import math
import string
import collections
from collections import Counter


def readints():
    return list(map(int, input().split()))


def nCr(n, r):
    return math.factorial(n)//(math.factorial(n-r)*math.factorial(r))


def has_duplicates2(seq):
    seen = []
    for item in seq:
        if not(item in seen):
            seen.append(item)
    return len(seq) != len(seen)


def divisor(n):
    divisor = []
    for i in range(1, n+1):
        if n % i == 0:
            divisor.append(i)
    return divisor


# coordinates
dx = [-1, -1, -1, 0, 0, 1, 1, 1]
dy = [-1, 0, 1, -1, 1, -1, 0, 1]


n, m = map(int, input().split())
print(n*(n-1)//2+m*(m-1)//2)


Verdicts: Runtime Error

Wrong Answer

Wrong Answer

Accepted