/in/foo.cc: In function 'int main()':
/in/foo.cc:7:2: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(a);
  ^~~~
In file included from /in/foo.cc:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:7:8: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(a);
        ^
In file included from /in/foo.cc:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:8:2: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(b);
  ^~~~
In file included from /in/foo.cc:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:8:8: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(b);
        ^
In file included from /in/foo.cc:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc: In function 'int Concat(char*, char*)':
/in/foo.cc:17:17: warning: left operand of comma operator has no effect [-Wunused-value]
  for(i=n-1,j=1;i<n+m-3,j<m;i++,j++)
                ~^~~~~~
/tmp/cctbpOst.o: In function `main':
foo.cc:(.text.startup+0x15): warning: the `gets' function is dangerous and should not be used.