static class Stack
    {
        int mytop;
        double stk[];
        
        public Stack(int num) {
            mytop=-1;
            stk=new double[num];
        }
        /*出栈*/
        double mypop()
        {
            double peek=stk[mytop];
            mytop--;
            return peek;
        }
        /*入栈*/
        void mypush(double x)
        {
            mytop++;
            stk[mytop]=x;
            
        }
        /*判空*/
        Boolean myisempty()
        {
            if(mytop==-1)
                return true;
            else
                return false;
        }
        /*取栈顶元素*/
        double mypeek()
        {
            double peek=stk[mytop];
            return peek;
        }
        /*栈大小*/
        int mysize()
        {
            return mytop+1;
        }
    }
    
    static class Tack
    {
        int mytop;
        String tk[];
        
        public Tack(int num) {
            mytop=-1;
            tk=new String[num];
        }
        /*出栈*/
        String mypop()
        {
            String peek=tk[mytop];
            mytop--;
            return peek;
        }
        /*入栈*/
        void mypush(String x)
        {
            mytop++;
            tk[mytop]=x;
            
        }
        /*判空*/
        Boolean myisempty()
        {
            if(mytop==-1)
                return true;
            else
                return false;
        }
        /*取栈顶元素*/
        String mypeek()
        {
            String peek=tk[mytop];
            return peek;
        }
        /*栈大小*/
        int mysize()
        {
            return mytop+1;
        }
    }