View Compilation Error

0_0_21648637_15004.cpp: In function 'int main()':
0_0_21648637_15004.cpp:18:5: error: 'cin' was not declared in this scope
     cin>>t;  
     ^
0_0_21648637_15004.cpp:26:29: error: 'memset' was not declared in this scope
         memset(v,0,sizeof(v));  
                             ^
0_0_21648637_15004.cpp:27:23: error: 'sort' was not declared in this scope
         sort(p,p+n,cmp);  
                       ^
0_0_21648637_15004.cpp:55:9: error: 'cout' was not declared in this scope
         cout<<sum<<endl;  
         ^
0_0_21648637_15004.cpp:55:20: error: 'endl' was not declared in this scope
         cout<<sum<<endl;  
                    ^