[BOJ] #10773 제로

 

 

 

 

import sys
n = int(sys.stdin.readline())

class stacking:
    def __init__(self):
        self.top = []

    def push(self, a):
        return self.top.append(a)
    
    def pop(self):
        if not self.top: 
            pass
        else:
            return self.top.pop()
    
    def ssum(self):
        return sum(self.top)
    
stack = stacking()

def solution(s):
    if s > 0 :
        stack.push(s)
    else:
        stack.pop()
        
for i in range(n):
    s = int(sys.stdin.readline())
    solution(s)
    
print(stack.ssum())