foo.cpp: In function 'int main()':
foo.cpp:6:1: error: 'cin' was not declared in this scope
 cin>>s>>t>>w;
 ^
foo.cpp:6:1: note: suggested alternative:
In file included from c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\mingw32\bits\stdc++.h:74:0,
                 from foo.cpp:1:
c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^
foo.cpp:23:3: error: 'cout' was not declared in this scope
   cout<<a[j];
   ^
foo.cpp:23:3: note: suggested alternative:
In file included from c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\mingw32\bits\stdc++.h:74:0,
                 from foo.cpp:1:
c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^