/in/foo.cc: In function 'void plusStr(char*, char*, char*)':
/in/foo.cc:14:11: warning: unused variable 'k' [-Wunused-variable]
   int i,j,k;
           ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:90:3: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   gets(s);
   ^~~~
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /usr/include/c++/6/ext/string_conversions.h:43,
                 from /usr/include/c++/6/bits/basic_string.h:5417,
                 from /usr/include/c++/6/string:52,
                 from /usr/include/c++/6/bits/locale_classes.h:40,
                 from /usr/include/c++/6/bits/ios_base.h:41,
                 from /usr/include/c++/6/ios:42,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:90:9: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   gets(s);
         ^
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /usr/include/c++/6/ext/string_conversions.h:43,
                 from /usr/include/c++/6/bits/basic_string.h:5417,
                 from /usr/include/c++/6/string:52,
                 from /usr/include/c++/6/bits/locale_classes.h:40,
                 from /usr/include/c++/6/bits/ios_base.h:41,
                 from /usr/include/c++/6/ios:42,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:97:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (i=0; i<strlen(s); i++)
              ~^~~~~~~~~~
/tmp/ccdHSalS.o: In function `main':
foo.cc:(.text.startup+0xcb): warning: the `gets' function is dangerous and should not be used.