任意の基準でソートして貪欲

C - Different Strokes

O(N)

import sys
import math
import heapq
import itertools
from collections import deque
from functools import reduce

# main
def main():
    N = int(input())
    BA = []

    for i in range(N):
        a, b = list(map(int, input().split()))
        BA.append([-a-b, a, b])
    BA.sort()

    ans=0
    for i in range(N):
        c, a, b = BA[i]
        if i%2 == 0:
            ans += a
        else:
            ans -= b
    print(ans)

# エントリポイント
if __name__ == '__main__':
    main()