foo.cc: In function 'int main()':
foo.cc:103:9: warning: unused variable 'n2' [-Wunused-variable]
  103 |  int n1,n2,n3,i;
      |         ^~
foo.cc:103:12: warning: unused variable 'n3' [-Wunused-variable]
  103 |  int n1,n2,n3,i;
      |            ^~
foo.cc:103:15: warning: unused variable 'i' [-Wunused-variable]
  103 |  int n1,n2,n3,i;
      |               ^

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