#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import array
import itertools
import math


def make_pyramid_seq(index):
    sequence = array.array("I", range(1, index + 1))
    sequence.extend(range(1, index)[::-1])
    return sequence


def solve(given_seq):
    given_sum = sum(given_seq)
    pyramid_seq = make_pyramid_seq(math.floor(math.sqrt(given_sum)))
    zip_iter = itertools.zip_longest(given_seq, pyramid_seq, fillvalue=0)
    return sum(max(0, act - ide) for act, ide in zip_iter)


def main():
    _ = input()
    given_seq = array.array("I", map(int, input().split()))
    print(solve(given_seq))


if __name__ == '__main__':
    main()