import sys, time, random
from collections import deque, Counter, defaultdict
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 63 - 1
mod = 998244353
sys.setrecursionlimit(10 ** 6 + 5)

n = ii()
s = input()

t = []

for v in s:
    if t and t[-1] =='-' and v == '-':
        t.pop()
        continue
    t.append(v)
t = ''.join(t)
print(eval(t))