foo.c: In function 'mis':
foo.c:8:44: error: 'key' undeclared (first use in this function)
    8 |             str[i] = 'a' + (str[i] - 'a' + key) % 26;
      |                                            ^~~
foo.c:8:44: note: each undeclared identifier is reported only once for each function it appears in
foo.c: In function 'main':
foo.c:16:12: error: invalid suffix "s" on integer constant
   16 |     char s[10000s];
      |            ^~~~~~
foo.c:16:10: warning: unused variable 's' [-Wunused-variable]
   16 |     char s[10000s];
      |          ^

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