foo.cc: In function 'int main()':
foo.cc:5:6: warning: unused variable 'i' [-Wunused-variable]
    5 |  int i,j,k,n;
      |      ^
foo.cc:5:8: warning: unused variable 'j' [-Wunused-variable]
    5 |  int i,j,k,n;
      |        ^
foo.cc:5:10: warning: unused variable 'k' [-Wunused-variable]
    5 |  int i,j,k,n;
      |          ^

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