#!/usr/bin/env python3

n = int(input())

min_balance = 0
curr_balance = 0

for i in range(n):
    delta = int(input())
    curr_balance += delta
    if curr_balance < min_balance:
        min_balance = curr_balance

if min_balance < 0:
    print(-1 * min_balance)
else:
    print(0)