1027B - Numbers on the Chessboard - CodeForces Solution

import sys

lst = sys.stdin.readlines()
n, q = map(int, lst[0].split())

for i in range(q):
    x, y = map(int, lst[i + 1].split())
    cnt = (x - 1) * n + y
    ans = (cnt + 1) // 2
    if ((x + y) % 2 == 1): ans += (n * n + 1) // 2
    sys.stdout.write(str(ans) + '\n')