foo.cc: In function 'int main()':
foo.cc:7:21: error: 'X1' was not declared in this scope; did you mean 'x1'?
    7 |         a=sqrt(pow((X1-X2),2)+pow((Y1-Y2),2));
      |                     ^~
      |                     x1
foo.cc:7:24: error: 'X2' was not declared in this scope; did you mean 'x2'?
    7 |         a=sqrt(pow((X1-X2),2)+pow((Y1-Y2),2));
      |                        ^~
      |                        x2
foo.cc:7:36: error: 'Y1' was not declared in this scope; did you mean 'y1'?
    7 |         a=sqrt(pow((X1-X2),2)+pow((Y1-Y2),2));
      |                                    ^~
      |                                    y1
foo.cc:7:39: error: 'Y2' was not declared in this scope; did you mean 'y2'?
    7 |         a=sqrt(pow((X1-X2),2)+pow((Y1-Y2),2));
      |                                       ^~
      |                                       y2
foo.cc:8:20: error: 'X3' was not declared in this scope; did you mean 'x3'?
    8 |     b=sqrt(pow((X1-X3),2)+pow((Y1-Y3),2));
      |                    ^~
      |                    x3
foo.cc:8:35: error: 'Y3' was not declared in this scope; did you mean 'y3'?
    8 |     b=sqrt(pow((X1-X3),2)+pow((Y1-Y3),2));
      |                                   ^~
      |                                   y3

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