N=int(input())
A=list(input().split())
A_num=[]
A_sym=[1]
for i in range(N):
    if A[i]=="+":
        A_sym.append(1)
    elif A[i]=="-":
        A_sym.append(0)
    else:
        A_num.append(int(A[i]))
num=(N+1)//2
ans=0
for i in range(num):
    if A_sym[i]==1:
        ans+=A_num[i]
    else:
        ans-=A_num[i]
print(ans)