foo.cc: In function 'int main()':
foo.cc:20:8: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   20 |  gets(a);
      |        ^
In file included from /usr/include/stdio.h:867,
                 from /usr/include/c++/9/cstdio:42,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:46,
                 from foo.cc:1:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:235:1: note: declared here
  235 | gets (char *__str)
      | ^~~~
foo.cc:20:8: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   20 |  gets(a);
      |        ^
In file included from /usr/include/stdio.h:867,
                 from /usr/include/c++/9/cstdio:42,
                 from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:46,
                 from foo.cc:1:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:235:1: note: declared here
  235 | gets (char *__str)
      | ^~~~
foo.cc:20:6: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result [-Wunused-result]
   20 |  gets(a);
      |  ~~~~^~~
/usr/bin/ld: /tmp/ccoyizjR.o: in function `main':
foo.cc:(.text.startup+0x25): warning: the `gets' function is dangerous and should not be used.

[Hydro](https://hydro.ac)提供评测服务