foo.cc: In function 'int main()':
foo.cc:7:14: error: 'i' was not declared in this scope
    7 |  for(int n=0;i<a;i++)
      |              ^
foo.cc:16:8: error: 'd' was not declared in this scope
   16 |  cout<<d;
      |        ^
foo.cc:15:9: warning: unused variable 'c' [-Wunused-variable]
   15 |  double c=1.0*b/a;
      |         ^

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