/in/foo.cc: In function 'void jk(int)':
/in/foo.cc:21:10: warning: right operand of comma operator has no effect [-Wunused-value]
  a1=a-1,b;
          ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:38:2: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(s1+1),len1=strlen(s1+1),x=1;
  ^~~~
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:46,
                 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:38:11: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(s1+1),len1=strlen(s1+1),x=1;
           ^
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:46,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/tmp/ccpR6hUZ.o: In function `main':
foo.cc:(.text.startup+0x16): warning: the `gets' function is dangerous and should not be used.