Problem:


Score : 100 points

Problem Statement

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.

Constraints

0 \leq N,M \leq 100

2 \leq N+M

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N M

Output

Print the answer.

Sample Input 1

2 1

Sample Output 1

1

For example, let us assume that the numbers written on the three balls are 1,2,4.

If we choose the two balls with 1 and 2, the sum is odd;

If we choose the two balls with 1 and 4, the sum is odd;

If we choose the two balls with 2 and 4, the sum is even.

Thus, the answer is 1.

Sample Input 2

4 3

Sample Output 2

9

Sample Input 3

1 1

Sample Output 3

0

Sample Input 4

13 3

Sample Output 4

81

Sample Input 5

0 3

Sample Output 5

3



Sample input:
2 1


Sample output:
1

Submission status: Accepted

Solution code:
def main(sample_file = ''):

    """ convenient functions
    # for i, a in enumerate(iterable)
    # q, mod = divmod(a, b)
    # divmod(x, y) returns the tuple (x//y, x%y)
    # Higher-order function: reduce(operator.mul, xyz_count, 1)
    # manage median(s) using two heapq https://atcoder.jp/contests/abc127/tasks/abc127_f
    """

    """convenient decorator
    # @functools.lru_cache():
    # to facilitate use of recursive function
        # ex:
        # from functools import lru_cache
        # import sys
        # sys.setrecursionlimit(10**9)
        # @lru_cache(maxsize=None)
        # def fib(n):
        #     if n < 2:
        #         return n
        #     return fib(n-1) + fib(n-2)
        # print(fib(1000))
    """
    
    # import numpy as np
    import sys
    sys.setrecursionlimit(10**7)
    from itertools import accumulate, combinations, permutations, product # https://docs.python.org/ja/3/library/itertools.html
    # accumulate() returns iterator! to get list: list(accumulate())
    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 = []  # prime factor
        b, e = 2, 0  # base, exponent
        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
        """
        # TODO: How should I do when n - r is negative?
        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 # https://docs.python.org/ja/3/library/collections.html#collections.deque
    from heapq import heapify, heappop, heappush, heappushpop, heapreplace,nlargest,nsmallest # https://docs.python.org/ja/3/library/heapq.html
    from copy import deepcopy, copy # https://docs.python.org/ja/3/library/copy.html
    import operator
    from operator import itemgetter #sort 
    # ex1: List.sort(key=itemgetter(1))
    # ex2: sorted(tuples, key=itemgetter(1,2))
    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 # Deprecated since version 3.5: Use math.gcd() instead.
    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)
    def make_divisors(n, reversed=False):
        """create list of divisors
        
        Args:
            number (int): number from which list of divisors is created
            reversed (bool, optional): ascending order if False. Defaults to False.
        
        Returns:
            list: list of divisors
        """
        divisors = set()
        for i in range(1, int(n**0.5)+1):
            if n % i == 0:
                divisors.add(i)
                divisors.add(n//i)
        return sorted(list(divisors),reverse=reversed)
    
    # first create factorial_list
    # fac_list = mod_factorial_list(n)
    INF = 10 ** 18
    MOD = 10 ** 9 + 7
    AtoZ = list('abcdefghijklmnopqrsruvwxyz')
    modpow = lambda a, n, p = MOD: pow(a, n, p) # Recursive function in python is slow!
    def modinv(a, p = MOD):
        # evaluate reciprocal using Fermat's little theorem:
        # a**(p-1) is identical to 1 (mod p) when a and p is coprime
        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):
        # fac_list = modfactorial_list(100)
        # print(modcomb(100, 5, modfactorial_list(100)))
        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))

    class UnionFindTree:
        """union find tree class
        TODO: fix this description...
        how to use (example):
        >>  uf = UnionFindTree(N) 
        >>  if uf.find_root(a) == uf.find_root(b):
        >>      do something
        >>  else:
        >>      do something
        >>      uf.unite(a, b)
        """
        def __init__(self, N):
            self.root = [-1] * (N+1)
            self.rank   = [0]  * (N+1)
            self.connected_num = [1] * (N+1)
    
        def find_root(self,x):
            root = self.root
            while root[x] != -1:
                x = root[x]
            return x
    
        def unite(self,x,y):
            root = self.root
            rank = self.rank
            connected_num = self.connected_num
            find_root = self.find_root
    
            rx = find_root(x)
            ry = find_root(y)
            if rx != ry:
                if rank[rx] < rank[ry]:
                    root[rx] = ry
                    rx,ry = ry,rx
                else:
                    if rank[rx] == rank[ry]:
                        rank[rx] += 1
                    root[ry] = rx       
                connected_num[rx] += connected_num[ry]

    # Graph: https://en.wikipedia.org/wiki/Directed_graph
    # Bellman-Ford: O(|V||E|). Use this if there exists an edge with negative length in the graph
    # After N steps, the shortest path has converded if there doesn't exist an cycle of edges with negative
    # Watch out: d[N] == d[2*N] doesn't necessarily mean the graph doesn't have negative cycle
    # ref: https://www.youtube.com/watch?v=1Z6ofKN03_Y

    def BellmanFord(N, M, ABC, vertex_start, vertex_end, value_if_inf = -1, find_shortest = False):
        """to calculate furthest or shortest length between vertex_start and vertex_end using BellmanFord algorithm
        
        Args:
            N (int): number of vertices
            M (int): number of edges
            ABC (list): [(ai, bi, ci) for _ in range(N)] where i-th edge is directed from vertex ai to vertex bi and the length is ci 
            vertex_start (int): start vertex. usually use 0.
            vertex_end (int): end vertex. usually use N-1.
            value_if_inf (int or string as you like, optional): value you want when the furthest (or shortest) distance is infinite (or -infinite). Defaults to -1.
            find_shortest (bool, optional): choose False to find furthest path. Defaults to False.
        
        Returns:
            int or string: normally int (but can be str if you set value_if_inf to str)
            
        Example:
                N, M, P = R()
                ABC = [R() for _ in range(M)]
                ABC = [(a-1, b-1, c-P) for a, b, c in ABC]
                print(BellmanFord(N, M, ABC, 0, N-1, value_if_inf = 'inf'))

        """

        def make_reachable_list(N, M, ABC, vertex_start, vertex_end):
            reachable_to_direct = defaultdict(list)
            reachable_from_direct = defaultdict(list)
            reachable_from_start = [False] * N
            reachable_to_end = [False] * N
            reachable_from_start[vertex_start] = True
            reachable_to_end[vertex_end] = True
            reachable_from_both_sides = [False] * N
            dfs_from_start = []
            dfs_to_end = []
            for a, b, c in ABC:
                reachable_to_direct[a].append(b)
                reachable_from_direct[b].append(a)
                if a == vertex_start:
                    dfs_from_start.append(b)
                    reachable_from_start[b] = True
                if b == vertex_end:
                    dfs_to_end.append(a)
                    reachable_to_end[a] = True
            while dfs_from_start:
                v = dfs_from_start.pop()
                for i in reachable_to_direct[v]:
                    if not reachable_from_start[i]:
                        reachable_from_start[i] = True
                        dfs_from_start.append(i)
            while dfs_to_end:
                v = dfs_to_end.pop()
                for i in reachable_from_direct[v]:
                    if not reachable_to_end[i]:
                        reachable_to_end[i] = True
                        dfs_to_end.append(i)
            for i in range(N):
                reachable_from_both_sides[i] = reachable_from_start[i] and reachable_to_end[i]
            return reachable_from_both_sides
        
        reachable_from_both_sides = make_reachable_list(N, M, ABC, vertex_start, vertex_end)
        
        if find_shortest:
            dist = [INF for i in range(N)]
        else:
            dist = [-INF for i in range(N)]
        
        dist[vertex_start] = 0
        for i in range(N):
            updated = False
            for a, b, c in ABC:
                if not reachable_from_both_sides[a]:
                    continue
                elif find_shortest:
                    update_condition = dist[a] + c < dist[b]
                else:
                    update_condition = dist[a] + c > dist[b]
                if dist[a] != INF and update_condition:
                    dist[b] = dist[a] + c
                    updated = True
                    if i == N-1:
                        return value_if_inf
            if not updated:
                break
        return dist[vertex_end]

    """ initialize variables and set inputs
    # initialize variables
        # to initialize list, use [0] * n
        # to initialize two dimentional array:
            # ex) [[0] * N for _ in range(N)]
            # ex2) dp = [[0] * (N+1) for _ in range(W*2)]
    # set inputs
        # put inputs between specific values (almost as quickly)
        # ex) S = [-INF] + [int(r()) for _ in range(A)] + [INF]
        # open(0).read() is sometimes useful:
        # ex) n, m, *x = map(int, open(0).read().split())
        #     min(x[::2]) - max(x[1::2])
        # ex2) *x, = map(int, open(0).read().split())
        #     don't forget to add comma after *x if only one variable is used
    # preprocessing
        # transpose = [x for x in zip(*data)]
        # ex) [[1, 2, 3], [4, 5, 6], [7, 8, 9]] => [(1, 4, 7), (2, 5, 8), (3, 6, 9)]
        # flat = [flatten for inner in data for flatten in inner]
        # ex) [[1, 2, 3], [4, 5, 6], [7, 8, 9]] => [1, 2, 3, 4, 5, 6, 7, 8, 9]
    # calculate and output
        # output pattern
        # ex1) print(*l) => when l = [2, 5, 6], printed 2 5 6
    """

    # functions to read input
    r = lambda: sys.stdin.readline().strip()
    r_int = lambda: int(r())
    r_float = lambda: float(r())
    R = lambda: list(map(int, r().split()))
    R_str = lambda: r().split()
    R_map = lambda: map(int, r().split())
    R_float = lambda: list(map(float, r().split()))
    R_tuple = lambda: tuple(map(int, r().split()))

    """ how to treat input
    # single int: int(r())
    # single string: r()
    # single float: float(r())
    # line int: R()
    # line string: r().split()
    # line (str, int, int): [j if i == 0 else int(j) for i, j in enumerate(r().split())]
    # lines int: [R() for _ in range(n)]
    """

    # for test
    if sample_file:
        sys.stdin = open(sample_file)
        
    # ----------------------------------
    # main
    #%%
    N, M = R()
    ans = 0
    ans += combinations_count(N, 2)
    ans += combinations_count(M, 2)
    print(ans)
    
    #%%
    # end of main
    # ----------------------------------

    """memo: how to use defaultdict of list
    # initialize
    Dic = defaultdict(list)
    # append / extend
    Dic[x].append(y)
    # three methods for loop: keys(), values(), items()
    for k, v in Dic.items():
    """
    
    """memo: how to solve binary problems
    # to make binary digits text
    >>> a = 5
    >>> bin_str_a = format(a, '#06b')
    >>> print(bin_str_a)
    0b0101 # first 2 strings (='0b') indicates it is binary
    """
    
    """memo: how to solve the problem
    creating simple test/answer
    greed
    simple dp
    graph
    """

if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
N,M=list(map(int,input().split()))
a=[2]*N+[1]*M
count=0
for i in range(len(a)):
  for j in range(i+1,len(a)):
    if((a[i]+a[j])%2==0):
      count+=1
print(count)

Submission status: Accepted

Solution code:
a1, b1 = map(int, input().split())
print(int(a1*(a1-1)/2)  +  int(b1*(b1-1)/2))

Submission status: Accepted

Solution code:
N, M=map(int, input().split())

if N <=1 and M<=1:
    print (0)
elif N>=2 and M<=1:
    print (N*(N-1)//2)
elif N<=1 and M>=2:
    print (M*(M-1)//2)
else:
    print ((N*(N-1)//2)+(M*(M-1)//2))

Submission status: Accepted

Solution code:
# -*- coding: utf-8 -*-
a, b = map(int, input().split())
cnt = 0

# 偶数
#if a != 0:
#    if a % 2 != 0:
#        a = a - 1

# 奇数


# 組み合わせ
nCr = {}

# https://qiita.com/derodero24/items/91b6468e66923a87f39f
def cmb(n, r):
    if r == 0 or r == n: return 1
    if r == 1: return n
    if (n, r) in nCr: return nCr[(n, r)]
    nCr[(n, r)] = cmb(n - 1, r) + cmb(n - 1, r - 1)
    return nCr[(n, r)]


#
if a > 1:
    cnt = cnt + cmb(a, 2)

if b > 1:
    cnt = cnt + cmb(b, 2)
print(cnt)

Submission status: Accepted

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

if (A > 1):
    a_sum = A * (A - 1) / 2
else:
    a_sum = 0
if (B > 1):
    b_sum = B * (B - 1) / 2
else:
    b_sum = 0

ans = a_sum + b_sum
print(int(ans))

Submission status: Accepted

Solution code:
n,m = map(int,input().split())
ans = 0
if n>0:
  ans += n*(n-1)//2
if m>0:
  ans += m*(m-1)//2
print(ans)

Submission status: Accepted

Solution code:
import math
n,m=map(int,input().split())

if n >=2 and m >=2:
    ans=(n*(n-1))//2 +(m*(m-1))//2
elif n>=2:
    ans=(n*(n-1))//2
elif m >=2:
    ans=(m*(m-1))//2
else:
    ans=0

print(ans)

Submission status: Accepted

Solution code:
# coding: utf-8
# Your code here!
from math import factorial as f
def ncr(n,r):
    if n<r:
        return 0
    return f(n)//((f(n-r))*(f(r)))
n,m=map(int,input().split())
x=(ncr(n+m,n))
y=ncr(m,2)
z=(ncr(n,2))
print((y+z))

Submission status: Accepted

Solution code:
N,M = map(int,input().split())
print(N*(N-1)//2+(M*(M-1))//2)

Submission status: Accepted

Solution code:
"""
"""

from math import factorial


def int_as_array(num): return list(map(int, [y for y in str(num)]))


def array_as_int(arr): return int(''.join(map(str, arr)))


def read_int(): return int(input())


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


def array_to_string(arr, sep=' '): return sep.join(map(str, arr))


def matrix_to_string(arr, sep=' '): return '[\n' + '\n'.join(
    [sep.join(map(str, row)) for row in arr]) + '\n]'


def combine(n, r):
    try:
        return (factorial(n) / factorial(n - r)) * (1 / r)
    except:
        return 0


def solve(N, M):
    choose_evens = combine(N, 2)
    choose_odds = combine(M, 2)
    return int(choose_evens + choose_odds)


N, M = read_array()
print(solve(N, M))

Submission status: Accepted

Solution code:
from math import factorial
def ncr(n,r):
    return factorial(n) // factorial(r) // factorial(n - r)

N, M = map(int, input().split())

n = 0
m = 0

if N > 1:
    n = ncr(N,2)
if M > 1:
    m = ncr(M,2)

print(n + m)

Submission status: Accepted

Solution code:
import sys
readline = sys.stdin.buffer.readline
from math import factorial
n,m = map(int,readline().split())

def combinations_count(n,r):
    """組み合わせnCr"""
    return factorial(n) // (factorial(n-r)*factorial(r))
ans1 = 0
ans2 = 0
if n >= 2:
    ans1 = combinations_count(n,2)
if m >= 2:
    ans2 = combinations_count(m,2)

print(ans1+ans2)

Submission status: Accepted

Solution code:
import math

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

if __name__ == "__main__":
    N, M = map(int, input().split())
    ret = 0
    if M >= 2:
        ret += combinations_count(M, 2)
    else:
        pass
    if N >= 2:
        ret += combinations_count(N, 2)
    else:
        pass
    print(ret)

Submission status: Accepted

Solution code:
n, m = map(int, input().split())

li_1 = [2 for i in range(n)]
li_2 = [1 for i in range(m)]
li = li_1 + li_2

res = 0
for i in range(len(li)):
    if len(li[i+1:]) >0:
        for j in li[i+1:]:
            if (li[i]+j)%2 == 0:
                res+=1

print(res)

Submission status: Accepted

Solution code:
import math

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

def comb(n, r):
    if n <= 1:
        return 0
    return perm(n, r)//math.factorial(r)

N, M = map(int,input().split(" "))

ans = comb(N,2) + comb(M,2)


print(int(ans))

Submission status: Accepted

Solution code:
m,n = map(int,input().split())
mC2 = int(m*(m-1) /2)
nC2 = int(n*(n-1)/2)

print(mC2 + nC2)

Submission status: Accepted

Solution code:
import math

f = math.factorial


def comb(n, r):
    if n < r:
        return 0
    else:
        return f(n) // f(r) // f(n - r)


N, M = map(int, input().split())
print(comb(N, 2) + comb(M, 2))

Submission status: Accepted

Solution code:
n,m= map(int,input().split())

ans=0
if n<2:
    pass
else:
    ans += (n*(n-1))//2
if m<2:
    pass
else:
    ans += (m*(m-1))//2
print(ans)

Submission status: Accepted

Solution code:
m, n = input().split()

def calc(num):
    sums = 0
    if num <=1:
        return 0
    for i in range(1, num):
        sums += i
    return sums

ms = calc(int(m))
ns = calc(int(n))
print(ms+ns)

Submission status: Accepted

Solution code:
N, M = map(int, input().split())
ans = 0
if N >= 2:
    for i in range(N):
        for j in range(i+1, N):
            ans += 1
if M >= 2:
    for i in range(M):
        for j in range(i+1, M):
            ans += 1
print(ans)

Submission status: Accepted

Solution code:
N, M = map(int, input().split())
print(int(((M+N)*(M+N-1))/2-(N*M)))

Submission status: Accepted

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

Submission status: Accepted

Solution code:
N,M=map(int,input().split())
ans=int((N*(N-1)+M*(M-1))/2)
print(ans)

Submission status: Accepted

Solution code:
from math import factorial


def main(a, b):
    ans = 0

    if a >= 2:
        ans += calc(a)
    if b >= 2:
        ans += calc(b)

    print(ans)


def calc(a):
    return factorial(a) // factorial(2) // factorial(a - 2)


if __name__ == "__main__":
    a, b = map(int, input().split())

    main(a, b)

Submission status: Accepted

Solution code:
import math
n,m=map(int,input().split())
count=0
if m==1 or n==1:
  count+=0
if n>1:
  count+= math.factorial(n)/(math.factorial(n-2)*2)
if m>1:
  count+= math.factorial(m)/(math.factorial(m-2)*2)
print(int(count))

Submission status: Accepted

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

Submission status: Accepted

Solution code:
import math
n,m=map(int, input().split())
def comb(n,r):
    return math.factorial(n) // (math.factorial(n-r) * math.factorial(r))
if n == 1 and m == 1:
    print(0)
elif n < 2 or m < 2:
    if n < 2:
        print(comb(m,2))
    else:
        print(comb(n,2))
else:
    n_comb = comb(n,2)
    m_comb = comb(m,2)
    print(n_comb+m_comb)

Submission status: Accepted

Solution code:
N, M = map(int, input().split())

even = N*(N-1)/2
odd = M*(M-1)/2

print(int(even + odd))

Submission status: Accepted

Solution code:
n,m = map(int,input().split())
##偶数+偶数(n+n)
n1 = n*(n-1)/2
##奇数+奇数(m+m)
m1 = m*(m-1)/2
##print
ans = int(n1 + m1)
print(ans)

Submission status: Accepted

Solution code:
n, m = map(int, input().split())

print(int(n * (n - 1) / 2 + m * (m - 1)/2))

Submission status: Accepted

Solution code:
N , M = map(int,input().split())

print(N*(N-1)//2+M*(M-1)//2)

Submission status: Accepted

Solution code:
import math

N, M = map(int, input().split())

if N < 2:
  even =0
else:
  even = math.factorial(N) // (math.factorial(N - 2) * math.factorial(2))

if M < 2:
  odd = 0
else:
  odd = math.factorial(M) // (math.factorial(M - 2) * math.factorial(2))

#print(even, odd)
print(even + odd)

Submission status: Accepted

Solution code:
import math

n, m =map(int,input().split())
if n <= 1:
  if m <= 1:
    ans = 0
  else:
    ans = math.factorial(m)//(math.factorial(m-2)* math.factorial(2)) 
elif m <= 1:
  ans = math.factorial(n)//(math.factorial(n-2) * math.factorial(2))
else:
  ans = math.factorial(n)//(math.factorial(n-2) * math.factorial(2)) +math.factorial(m)//(math.factorial(m-2)* math.factorial(2)) 
print(ans)

Submission status: Accepted

Solution code:


n, m = map(int, input().split())

import math
def combinations_count(n, r):
    if n < r:
        return 0
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

print(combinations_count(n, 2) + combinations_count(m, 2))

Submission status: Accepted

Solution code:
import math
s = input().split()
n=int(s[0])
k=int(s[1])
result=0
if n>1:
    result+=math.factorial(n)/math.factorial(2)/math.factorial(n-2)
if k>1:
    result+=math.factorial(k)/math.factorial(2)/math.factorial(k-2)
print(int(result))

Submission status: Accepted

Solution code:
import math
def nCr(n, r): 
  
    return (math.factorial(n) // (math.factorial(r)  
                * math.factorial(n - r))) 
n,m=list(map(int,input().split()))
total=0
if n>1:
  total+=nCr(n,2)
if m>1:
  total+=nCr(m,2)
print(total)

Submission status: Accepted

Solution code:
n, m = map(int, input().split())
all_count = (n + m) * (n + m - 1) // 2
odd_count = m * n

print(all_count - odd_count)

Submission status: Accepted

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

ret = 0
ret = ret + (int)((a * (a-1)) / 2)
ret = ret + (int)((b * (b-1)) / 2)

print("{}".format(ret))

Submission status: Accepted

Solution code:
import math


n, m = map(int, input().split())


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


ans = 0
if n > 1:
    ans += combinations_count(n, 2)
if m > 1:
    ans += combinations_count(m, 2)

print(ans)

Submission status: Accepted

Solution code:
n, m = map(int, input().split())
oo = n * (n-1) / 2
ee = m * (m-1) / 2

print(int(oo + ee))

Submission status: Accepted

Solution code:
n,m = map(int,input().split())

n = (n * (n-1)) / (2 * 1)
m = (m * (m-1)) / (2 * 1)
#print(n)
#print(m)
print(int(n+m))

Submission status: Accepted

Solution code:
N, M = map(int, input().split())
result = (N + M) * (N + M - 1) / 2 - (N * M)
print(int(result))

Submission status: Accepted

Solution code:
N, M = map(int, input().split())
 
nCr = {}
def cmb(n, r):
    if r == 0 or r == n: return 1
    if r == 1: return n
    if (n,r) in nCr: return nCr[(n,r)]
    nCr[(n,r)] = cmb(n-1,r) + cmb(n-1,r-1)
    return nCr[(n,r)]

if N < 2 and M < 2:
  a = 0
elif N < 2:
  a = cmb(M,2)
elif M < 2:
  a = cmb(N,2)
elif N > 1 and M > 1:
  a = cmb(N,2) + cmb(M,2)

print(int(a))

Submission status: Accepted

Solution code:
even, odd = [int(x) for x in input().split(' ')]

even_comb = int(even * (even - 1) / 2)
odd_comb = int(odd * (odd - 1) / 2)

print(even_comb + odd_comb)

Submission status: Accepted

Solution code:
from operator import mul
from functools import reduce

def cmb(n,r):
    r = min(n-r,r)
    if r == 0: return 1
    over = reduce(mul, range(n, n - r, -1))
    under = reduce(mul, range(1,r + 1))
    return over // under


if __name__ == '__main__':
    a,b = map(int, input().split())
    c = 0
    d = 0
    if a > 1:
        c = cmb(a,2)
    if b > 1:
        d = cmb(b,2)
    print(c+d)

Submission status: Accepted

Solution code:
n,m =map(int,input().split())
def fx(x) :
    ans = 0
    for i in range(1,x):
        ans += i
    return ans
print(fx(n) + fx(m))

Submission status: Accepted

Solution code:
n,m = map(int,input().split())
a = 0
if n != 0:
    a = int(n*(n-1)/2)
if m != 0:
    a += int(m*(m-1)/2)
print(a)

Submission status: Accepted

Solution code:
n, m = map(int, input().split())

ans = ((n * (n-1)) // 2) + ((m * (m-1)) // 2)
print(ans)

Submission status: Accepted

Solution code:
N,M=map(int,input().split())
A=(N*(N-1))/2
B=(M*(M-1))/2
sum=int(A)+int(B)
print(int(sum))

Submission status: Accepted

Solution code:
N, A = map(int, input().split())

p = int(N * (N - 1) / 2)
q = int(A * (A - 1) / 2)
r = p + q
print(r)

Submission status: Accepted

Solution code:
import math
N,M=input().split()
N=int(N)
M=int(M)

if N>=2:
    E=(N-1)*N/2
else:
    E=0
if M>=2:
    O=M*(M-1)/2
else:
    O=0

print(round(E+O))

Submission status: Accepted

Solution code:
n,m = [int(i) for i in input().split()]
if n <= 1:
  a = 0
else:
  a = n*(n-1)/2
if m <= 1:
  b = 0
else:
  b = m*(m-1)/2
print(int(a+b))

Submission status: Accepted

Solution code:
N,M=map(int,input().split())

N1=(N*(N-1))/2
M1=(M*(M-1))/2

if N==0:
    print(int(M1))
elif M==0:
    print(int(N1))
else:
    print(int(M1+N1))

Submission status: Accepted

Solution code:
import math

n, m = map(int, input().split())

ns = [2] * n
ms = [3] * m

cnt = 0
for ni in ns:
  for mi in ms:
    s = ni + mi
    if s%2 == 0:
      cnt += 1

def combinations_count(n, r):
    if r > n: return 0
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))
      
nc = combinations_count(len(ns), 2)
mc = combinations_count(len(ms), 2)

print(cnt+nc+mc)

Submission status: Accepted

Solution code:
N,M = map(int, input().split())

print(N*(N-1)//2+M*(M-1)//2)

Submission status: Accepted

Solution code:
from math import factorial as fact
n,m=map(int,input().split())
i,k=0,0
if n<2 and m<2:
  print(0)
else:
  if n==0:i=0
  elif n==2:
  	i=1
  elif n!=1:
    i=fact(n)/fact(2)/fact(n-2)
  if m==0:k=0
  elif m==2:
  	k=1
  elif m!=1:
    k=fact(m)/fact(2)/fact(m-2)
  print(int(i+k))

Submission status: Accepted

Solution code:
n, m = map(int, input().split())

print(int((n+m)*(n+m-1)/2 - n*m))

Submission status: Accepted

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

Submission status: Accepted

Solution code:
n,m=map(int,input().split());print((n*~-n+m*~-m)//2)

Submission status: Accepted

Solution code:
from math import factorial
 
N, M = map(int, input().split())
if N != 0 and M != 0 and N != 1 and M != 1:
  Ncon = factorial(N) // factorial(2) // factorial(N - 2)
  Mcon = factorial(M) // factorial(2) // factorial(M - 2)
  print(Ncon+Mcon)
if N ==0 or N == 1:
  if M!=1:
    print(factorial(M) // factorial(2) // factorial(M - 2))
if M == 0 or M==1:
  if N!=1:
    print(factorial(N) // factorial(2) // factorial(N - 2))
if N==1 and M==1:
  print(0)

Submission status: Accepted

Solution code:
import math
def C(n, r):
    if n-r < 0:
        return 0
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))
N, M = map(int,input().split())
print (C(N,2)+C(M,2))

Submission status: Accepted

Solution code:
N, M = map(int, input().split())
ans = 0
tmp = 0
for i in reversed(range(1, N)):
    tmp += i
ans += tmp
tmp = 0
for i in reversed(range(1, M)):
    tmp += i
ans += tmp
print(ans)

Submission status: Accepted

Solution code:
import math

N, M = map(int, input().split())

c = 0

if(N > 1):
    c +=  math.factorial(N)/(math.factorial(N-2)*math.factorial(2))
if(M > 1):
    c += math.factorial(M)/(math.factorial(M-2)*math.factorial(2))

print(int(c))