foo.cpp: In function 'int mian()':
foo.cpp:12:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^
foo.cpp:11:8: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<ans<<endl;
        ^
c:/mingw/bin/../lib/gcc/mingw32/4.8.1/../../../libmingw32.a(main.o):(.text.startup+0xa7): undefined reference to `WinMain@16'
collect2.exe: error: ld returned 1 exit status