View Compilation Error

0_0_14564137_22686.cpp:1:7: error: expected nested-name-specifier before 'System'
 using System;
       ^
0_0_14564137_22686.cpp:20:5: error: expected ';' after class definition
     }
     ^
0_0_14564137_22686.cpp: In static member function 'static void ACMCS::HDU1001::Main()':
0_0_14564137_22686.cpp:9:13: error: 'string' was not declared in this scope
             string c; 
             ^
0_0_14564137_22686.cpp:11:21: error: 'c' was not declared in this scope
             while ((c = Console.ReadLine()) != null)
                     ^
0_0_14564137_22686.cpp:11:25: error: 'Console' was not declared in this scope
             while ((c = Console.ReadLine()) != null)
                         ^
0_0_14564137_22686.cpp:11:48: error: 'null' was not declared in this scope
             while ((c = Console.ReadLine()) != null)
                                                ^
0_0_14564137_22686.cpp:13:21: error: 'Convert' was not declared in this scope
                 n = Convert.ToInt32(c);
                     ^