Task 3 – Machine

#include <iostream>
#include <string>
#include <vector>
void sum(std::vector<std::string>& input) {

	int sum = 0;
	int numberA = std::stoi(*(input.end() - 1));
	input.pop_back();
	int numberB = std::stoi(*(input.end() - 1));
	input.pop_back();
	sum = numberA + numberB;
	std::string number = std::to_string(sum);
	input.push_back(number);
}
void subtract(std::vector<std::string>& input) {

	int sum = 0;
	int numberA = std::stoi(*(input.end() - 1));
	input.pop_back();
	int numberB = std::stoi(*(input.end() - 1));
	input.pop_back();
	sum = numberA - numberB;
	std::string number = std::to_string(sum);
	input.push_back(number);
}
void concat(std::vector<std::string>& input) {
	std::string numberA = *(input.end() - 1);
	input.pop_back();
	std::string numberB = (*(input.end() - 1));
	input.pop_back();
	std::string number = numberB+numberA;
	input.push_back(number);
}
void print(const std::vector<std::string>& forPrint) {

	for (std::string i : forPrint) {
		std::cout << i<<std::endl;
	}
}
int main (){
	std::string line;
	std::vector<std::string> inputContainer;
	while (line != "end") {

		std::cin >> line;
		inputContainer.push_back(line);
		if (line == "sum") {
			inputContainer.pop_back();
			sum(inputContainer);
		}
		else if (line == "subtract") {
			inputContainer.pop_back();
			subtract(inputContainer);
		}
		else if (line == "concat") {
			inputContainer.pop_back();
			concat(inputContainer);
		}
		else if (line == "discard") {
			inputContainer.pop_back();
			if (!inputContainer.empty()) {
				inputContainer.pop_back();
			}
		}

	}
		inputContainer.pop_back();
		print(inputContainer);

	return 0;
}