/in/foo.cc: In function 'bool solve()':
/in/foo.cc:136:3: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   gets(buf); buf_len=strlen(buf);
   ^~~~
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /in/foo.cc:2:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:136:11: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   gets(buf); buf_len=strlen(buf);
           ^
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /in/foo.cc:2:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:147:3: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   gets(buf); buf_len=strlen(buf);
   ^~~~
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /in/foo.cc:2:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:147:11: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   gets(buf); buf_len=strlen(buf);
           ^
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /in/foo.cc:2:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/tmp/ccCBIKSa.o: In function `solve()':
foo.cc:(.text+0xa4a): warning: the `gets' function is dangerous and should not be used.