foo.cc: In function 'int main()':
foo.cc:5:6: warning: unused variable 'i' [-Wunused-variable]
    5 |  int i,j,k;
      |      ^
foo.cc:8:10: warning: 'i' may be used uninitialized in this function [-Wmaybe-uninitialized]
    8 |  for(int i;i<=n;i++)
      |          ^

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