import math

def rpn(tokens):
    stack = []

    # Iterate through each token in the list of tokens
    for token in tokens:
        # Check if the token is an operator (+, -, *, /)
        if token in "+-*/":
            # Pop the last two numbers from the stack
            number2 = stack.pop()
            number1 = stack.pop()

            # Perform the arithmetic operation based on the operator
            if token == "+":
                result = number1 + number2
            elif token == "-":
                result = number1 - number2
            elif token == "*":
                result = number1 * number2
            else:  # token == "/"
                result = math.trunc(number1 / number2)

            # Push the result back onto the stack
            stack.append(result)
        else:
            # If the token is a number, convert it to an integer and push onto the stack
            stack.append(int(token))

    # The final result will be the only item remaining on the stack
    return stack.pop()


# Driver code
def main():
    inputs = [
        ["2", "1", "+", "3", "*"],  # (2 + 1) * 3 = 9
        ["4", "13", "5", "/", "+"],  # 4 + (13 / 5) = 6
        ["10", "6", "9", "3", "/", "-", "*"],  # (10 * (6 - (9 / 3))) = 30
        ["1", "1", "+", "2", "*"],  # (1 + 1) * 2 = 4
        ["3", "5", "8", "*", "+", "13", "-"],  # (3 + (5 * 8)) - 13 = 30
    ]

    for i in range(len(inputs)):
        print(i + 1, ". Input tokens = ", inputs[i], sep="")
        print("   Result = ", rpn(inputs[i]), sep="")
        print("-" * 100)


if __name__ == "__main__":
    main()