foo.cc: In function 'int main()':
foo.cc:47:9: warning: unused variable 'i' [-Wunused-variable]
   47 |     int i, j, u, v;
      |         ^
foo.cc:47:12: warning: unused variable 'j' [-Wunused-variable]
   47 |     int i, j, u, v;
      |            ^
foo.cc:47:15: warning: unused variable 'u' [-Wunused-variable]
   47 |     int i, j, u, v;
      |               ^
foo.cc:47:18: warning: unused variable 'v' [-Wunused-variable]
   47 |     int i, j, u, v;
      |                  ^

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