View Compilation Error

0_0_20110625_12198.c: In function 'main':
0_0_20110625_12198.c:5:2: error: too few arguments to function 'gets_s'
  gets_s(a);
  ^
In file included from GCC4.9.2/x86_64-w64-mingw32/include/stdio.h:959:0,
                 from 0_0_20110625_12198.c:1:
GCC4.9.2/x86_64-w64-mingw32/include/sec_api/stdio_s.h:91:25: note: declared here
   _CRTIMP char* __cdecl gets_s(char*,rsize_t);
                         ^