foo.cc: In function 'void SetUnion(int, int, int*, int*)':
foo.cc:26:21: warning: unused variable 'k' [-Wunused-variable]
   26 |     int i, j, c[N], k = 0;
      |                     ^
foo.cc: In function 'int main()':
foo.cc:37:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   37 |     scanf("%d %d %d", &m, &n, &p);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:39:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   39 |         scanf("%d", &a[i]);
      |         ~~~~~^~~~~~~~~~~~~
foo.cc:41:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   41 |         scanf("%d", &b[i]);
      |         ~~~~~^~~~~~~~~~~~~
foo.cc:43:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   43 |         scanf("%d", &c[i]);
      |         ~~~~~^~~~~~~~~~~~~

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