# import sys; input = sys.stdin.buffer.readline
# sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N = int(input())
	A = list(input().split())
	ans = int(A[0])
	val = []
	for i in range(1, N):
		if A[i] == "+":
			ans += val.pop()
		elif A[i] == "-":
			ans -= val.pop()
		else:
			val.append(int(A[i]))

	print(ans)


if __name__ == '__main__':
	main()