//构建单调辅助栈

class MinStack {
public:

    stack<int> stk, min_stk;

    /** initialize your data structure here. */
    MinStack() {

    }

    void push(int x) {
        stk.push(x);
        if(min_stk.empty() || min_stk.top() >= x)
            min_stk.push(x);
    }

    void pop() {
        if(stk.top() == min_stk.top())
            min_stk.pop();
        stk.pop();
    }

    int top() {
        return stk.top();
    }

    int getMin() {
        return min_stk.top();
    }
};

/**
 * Your MinStack object will be instantiated and called as such:
 * MinStack obj = new MinStack();
 * obj.push(x);
 * obj.pop();
 * int param_3 = obj.top();
 * int param_4 = obj.getMin();
 */