foo.cc: In function 'int main()':
foo.cc:11:19: error: 'a' was not declared in this scope
   11 |         int pos = a[n/2];
      |                   ^
foo.cc:6:13: warning: unused variable 'sumy' [-Wunused-variable]
    6 |         int sumy = 0;
      |             ^~~~

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