foo.c: In function 'concat':
foo.c:6:27: error: expected ';' before 'a'
    6 |           a[i+lena-1]=b[i]
      |                           ^
      |                           ;
    7 |   a[i+lena]=0;
      |   ~                        
foo.c: In function 'main':
foo.c:14:4: warning: 'gets' is deprecated [-Wdeprecated-declarations]
   14 |    gets(a);
      |    ^~~~
In file included from foo.c:1:
/nix/store/linb70pgp53f0kygxm5wk163dx22d681-glibc-2.37-45-dev/include/stdio.h:605:14: note: declared here
  605 | extern char *gets (char *__s) __wur __attribute_deprecated__;
      |              ^~~~
foo.c:15:4: warning: 'gets' is deprecated [-Wdeprecated-declarations]
   15 |    gets(b);
      |    ^~~~
/nix/store/linb70pgp53f0kygxm5wk163dx22d681-glibc-2.37-45-dev/include/stdio.h:605:14: note: declared here
  605 | extern char *gets (char *__s) __wur __attribute_deprecated__;
      |              ^~~~

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