<gh_stars>0
#!/usr/bin/env python3
# SPDX-FileCopyrightText: 2020 <NAME> <https://github.com/nfitzen>
#
# SPDX-License-Identifier: CC0-1.0

import itertools

with open('input.txt') as f:
    data = f.readlines()

data = list(map(int, data))

for n in enumerate(data[25:], 25):
    if n[1] not in (a + b for a, b in itertools.combinations(data[n[0]-25:n[0]], 2)):
        print(n[1])
        break
