栈练习3

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<stack>
 4 using namespace std;
 5 int n,k,a;
 6 int main()
 7 {
 8     stack<int>ss; 
 9     cin>>n;
10     while(n--)
11     {
12         cin>>k;
13         if(k==1)
14         {
15             cin>>a;
16             ss.push(a);
17         }
18         if(k==2)
19         {
20             ss.pop();
21         }
22         if(k==3)
23         {
24             cout<<ss.top()<<endl;
25         }
26     }
27     return 0;
28  }