/in/foo.cc: In function 'int main()':
/in/foo.cc:12:9: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(a1);gets(b1);
         ^
In file included from /usr/include/c++/7/cstdio:42:0,
                 from /usr/include/c++/7/ext/string_conversions.h:43,
                 from /usr/include/c++/7/bits/basic_string.h:6159,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/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:12:18: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(a1);gets(b1);
                  ^
In file included from /usr/include/c++/7/cstdio:42:0,
                 from /usr/include/c++/7/ext/string_conversions.h:43,
                 from /usr/include/c++/7/bits/basic_string.h:6159,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/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:8:44: warning: unused variable 'j' [-Wunused-variable]
  int a[100],b[100],c[100],lena,lenb,lenc,i,j,x;
                                            ^
/tmp/ccWl77O5.o: In function `main':
foo.cc:(.text.startup+0x56): warning: the `gets' function is dangerous and should not be used.