using System.Collections;
Stack s = new Stack();
s.Push("John");
s.Push("Richard");
s.Push("Sophia");
s.Pop(); s.Peek(); //read one from the start, but not delete it
using System.Collections.Generic;
Stack<string> s = new Stack<string>();
s.Push("John");
s.Push("Richard");
s.Push("Sophia");
string str = s.Pop(); //str="Sophia"
s.Count; //2
s.Contains("Sohpia"); //false