foo.cc: In function 'int sort(int*, int)':
foo.cc:20:1: warning: no return statement in function returning non-void [-Wreturn-type]
   20 | }
      | ^
foo.cc: In function 'int MergeSub(int*, int)':
foo.cc:25:37: error: 'j' was not declared in this scope
   25 |                 if (a[i] > a[i + 1])j++;
      |                                     ^
foo.cc:26:21: error: 'j' was not declared in this scope
   26 |                 if (j % 2 == 0)sort(a, j - 1);
      |                     ^
foo.cc:28:1: warning: no return statement in function returning non-void [-Wreturn-type]
   28 | }
      | ^
foo.cc: In function 'int main()':
foo.cc:33:17: error: 'n' was not declared in this scope; did you mean 'nb'?
   33 |         scan(a, n);
      |                 ^
      |                 nb

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