View Compilation Error

0_0_19172149_23410.cpp: In function 'int main()':
0_0_19172149_23410.cpp:12:19: error: too few arguments to function 'char* gets_s(char*, rsize_t)'
         gets_s(str);
                   ^
In file included from GCC4.9.2/x86_64-w64-mingw32/include/stdio.h:959:0,
                 from 0_0_19172149_23410.cpp: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);
                         ^
0_0_19172149_23410.cpp:15:37: error: 'strlen' was not declared in this scope
             for(int i=1;i<strlen(str);i++){
                                     ^