#!/usr/bin/python3

input() # Počet operací nepotřebujeme
tokens = input().split(" ")

stack = []
for token in tokens:
    if token == '+':
        y, x = stack.pop(), stack.pop()
        stack.append(x+y)
    elif token == '-':
        y, x = stack.pop(), stack.pop()
        stack.append(x-y)
    elif token == '*':
        y, x = stack.pop(), stack.pop()
        stack.append(x*y)
    elif token == '/':
        y, x = stack.pop(), stack.pop()
        stack.append(x//y)
    else:
        stack.append(int(token))

print(stack[0])