foo.cc: In function ‘int main()’:
foo.cc:8:19: error: ‘x’ was not declared in this scope
    8 |         for(int i=x;i<=y;i++)a[++n]=i;
      |                   ^
foo.cc:8:24: error: ‘y’ was not declared in this scope
    8 |         for(int i=x;i<=y;i++)a[++n]=i;
      |                        ^