Dcoder Cashback Question Incorrect Approach

cashback.py

from functools import cmp_to_key

n = int(input())

costs = []

for _ in range(n):
    c, x = input().split()
    costs.append((int(c), int(x)))
    
def getCost(seq):
    curr = 0
    debt = 0
    for c, x in seq:
        curr -= c
        if curr < 0:
            debt -= curr
            curr = 0
        curr += x - curr
    return debt
    
def cmp(p1, p2):
    c1, x1 = p1
    c2, x2 = p2
    f = c1 + max(c2 - x1, 0)
    s = c2 + max(c1 - x2, 0)
    if f < s:
        return -1
    elif f > s:
        return 1
    return -1 if x1 - c1 >= x2 - c2 else 1
    
costs.sort(key = cmp_to_key(cmp))

print(getCost(costs))