class Solution {
public:
    int calPoints(vector<string>& ops) {
        stack<int> stack;
        int sum =  0;
        
        for (int i = 0; i < ops.size(); i++){
            if (ops[i] == "+"){
                int first = stack.top();
                stack.pop();
                
                int second = stack.top();
                
                stack.push(first);
                
                stack.push(first + second);
                
                sum += first + second;
            }
            
            else if (ops[i] == "D"){
                sum += 2 * stack.top();
                stack.push(2 * stack.top());
            }
            
            else if (ops[i] == "C"){
                sum -= stack.top();
                stack.pop();
            }
            
            else{
                sum += stoi(ops[i]);
                stack.push(stoi(ops[i]));
            }
        }
        
        return sum;
        
        
    }
};