Buggy python submission (verdict: Runtime Error):
class Stack:
    MAX = 100

    def __init__(self):
        self.S = [None] * self.__class__.MAX
        self.top = 0

    def is_empty(self):
        return self.top == 0

    def is_full(self):
        return self.top >= self.__class__.MAX - 1

    def push(self, x):
        self.top += 1
        self.S[self.top] = x

    def pop(self):
        self.top -= 1
        return self.S[self.top + 1]


arr = [str(s) for s in input().split()]
stack = Stack()
for s in arr:
    if s in ["+", "-", "*"]:
        stack.push(
            eval("".join(map(str, [stack.pop(), s, stack.pop()][::-1]))))
    else:
        stack.push(int(s))

print(stack.pop())



Fixed submission:
class Stack:
    MAX = 101

    def __init__(self):
        self.S = [None] * self.__class__.MAX
        self.top = 0

    def is_empty(self):
        return self.top == 0

    def is_full(self):
        return self.top >= self.__class__.MAX - 1

    def push(self, x):
        self.top += 1
        self.S[self.top] = x
        return x

    def pop(self):
        self.top -= 1
        return self.S[self.top + 1]


stack = Stack()
print([stack.push(eval("".join(map(str,[stack.pop(),s,stack.pop()][::-1]))))
       if s in["+","-","*"]else stack.push(int(s))for s in input().split()][-1])

Buggy python submission (verdict: Runtime Error):
class Stack:
    MAX = 101

    def __init__(self):
        self.S = [None] * self.__class__.MAX
        self.top = 0

    def is_empty(self):
        return self.top == 0

    def is_full(self):
        return self.top >= self.__class__.MAX - 1

    def push(self, x):
        self.top += 1
        self.S[self.top] = x

    def pop(self):
        self.top -= 1
        return self.S[self.top + 1]


arr = [str(s) for s in input().split()]
stack = Stack()
stack.push(eval("".join(map(str, [stack.pop(), s, stack.pop()][::-1]))))
    if s in["+", "-", "*"] else stack.push(int(s)) for s in arr
print(stack.pop())



Fixed submission:
class Stack:
    MAX = 101

    def __init__(self):
        self.S = [None] * self.__class__.MAX
        self.top = 0

    def is_empty(self):
        return self.top == 0

    def is_full(self):
        return self.top >= self.__class__.MAX - 1

    def push(self, x):
        self.top += 1
        self.S[self.top] = x
        return x

    def pop(self):
        self.top -= 1
        return self.S[self.top + 1]


stack = Stack()
print([stack.push(eval("".join(map(str,[stack.pop(),s,stack.pop()][::-1]))))
       if s in["+","-","*"]else stack.push(int(s))for s in input().split()][-1])

Buggy python submission (verdict: Runtime Error):
class Stack:
    MAX = 101

    def __init__(self):
        self.S = [None] * self.__class__.MAX
        self.top = 0

    def is_empty(self):
        return self.top == 0

    def is_full(self):
        return self.top >= self.__class__.MAX - 1

    def push(self, x):
        self.top += 1
        self.S[self.top] = x

    def pop(self):
        self.top -= 1
        return self.S[self.top + 1]


stack = Stack()
[stack.push(eval("".join(map(str, [stack.pop(), s, stack.pop()][::-1]))))
 if s in["+", "-", "*"]else stack.push(int(s)) for s in str(s) for s in input().split()]
print(stack.pop())



Fixed submission:
class Stack:
    MAX = 101

    def __init__(self):
        self.S = [None] * self.__class__.MAX
        self.top = 0

    def is_empty(self):
        return self.top == 0

    def is_full(self):
        return self.top >= self.__class__.MAX - 1

    def push(self, x):
        self.top += 1
        self.S[self.top] = x
        return x

    def pop(self):
        self.top -= 1
        return self.S[self.top + 1]


stack = Stack()
print([stack.push(eval("".join(map(str,[stack.pop(),s,stack.pop()][::-1]))))
       if s in["+","-","*"]else stack.push(int(s))for s in input().split()][-1])

Buggy python submission (verdict: Runtime Error):
class Stack:
    MAX = 101

    def __init__(self):
        self.S = [None] * self.__class__.MAX
        self.top = 0

    def is_empty(self):
        return self.top == 0

    def is_full(self):
        return self.top >= self.__class__.MAX - 1

    def push(self, x):
        self.top += 1
        self.S[self.top] = x

    def pop(self):
        self.top -= 1
        return self.S[self.top + 1]


stack = Stack()
[stack.push(eval("".join(map(str, [stack.pop(), s, stack.pop()][::-1]))))
 if s in["+", "-", "*"]else stack.push(int(s)) for s in str(s) for s in [str(s) for s in input().split()]]
print(stack.pop())



Fixed submission:
class Stack:
    MAX = 101

    def __init__(self):
        self.S = [None] * self.__class__.MAX
        self.top = 0

    def is_empty(self):
        return self.top == 0

    def is_full(self):
        return self.top >= self.__class__.MAX - 1

    def push(self, x):
        self.top += 1
        self.S[self.top] = x
        return x

    def pop(self):
        self.top -= 1
        return self.S[self.top + 1]


stack = Stack()
print([stack.push(eval("".join(map(str,[stack.pop(),s,stack.pop()][::-1]))))
       if s in["+","-","*"]else stack.push(int(s))for s in input().split()][-1])