20250525

arr=input().split()
stack=[]

for i in range(0,len(arr)) :
    if arr[i]=='+' :
        w=stack[-1]+stack[-2]
        stack.pop()
        stack.pop()
        stack.append(w)
    elif arr[i]=='-' :
        w=stack[-2]-stack[-1]
        stack.pop()
        stack.pop()
        stack.append(w)