Untitled

#include<bits/stdc++.h>
using namespace std;

int solution(string &s) {
    int min = 0, max = (1 << 20) - 1;
    stringstream stream(s);
    stack<int> numberStack;
    string token;
    while (stream >> token) {
        if (token == "DUP") {
            if (!numberStack.size()) {
                return -1;
            }
            int x = numberStack.top();
            numberStack.push(x);
            continue;
        }
        if (token == "POP") {
            if (!numberStack.size()) {
                return -1;
            }
            numberStack.pop();
            continue;
        }
        if (token == "+") {
            if (numberStack.size() < 2) {
                return -1;
            }
            int x = numberStack.top();
            numberStack.pop();
            x += numberStack.top();
            numberStack.pop();
            if (x > max) {
                return -1;
            }
            numberStack.push(x);
            continue;
        }
        if (token == "-") {
            if (numberStack.size() < 2) {
                return -1;
            }
            int x = numberStack.top();
            numberStack.pop();
            x = numberStack.top() - x;
            numberStack.pop();
            if (x > max or x < min) {
                return -1;
            }
            numberStack.push(x);
            continue;
        }
        numberStack.push(stoi(token));
    }
}