/in/foo.cc: In function 'int main()':
/in/foo.cc:10:2: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(c);
  ^~~~
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:10:8: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(c);
        ^
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:11:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = 0; i < strlen(c); i++)
              ~~^~~~~~~~~~~
/in/foo.cc:7:16: warning: unused variable 'j' [-Wunused-variable]
  int i, n = 0, j = 0;
                ^
/tmp/ccR5xakp.o: In function `main':
foo.cc:(.text.startup+0x14): warning: the `gets' function is dangerous and should not be used.