View Compilation Error

0_0_26764144_8889.cpp: In function 'int main()':
0_0_26764144_8889.cpp:7:2: error: 'cin' was not declared in this scope
  cin>>r;
  ^
0_0_26764144_8889.cpp:7:2: note: suggested alternative:
In file included from 0_0_26764144_8889.cpp:2:0:
GCC4.9.2/x86_64-w64-mingw32/include/c++/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^