foo.c: In function 'Div':
foo.c:28:10: error: 'false' undeclared (first use in this function); did you mean 'fclose'?
   flag = false;
          ^~~~~
          fclose
foo.c:28:10: note: each undeclared identifier is reported only once for each function it appears in
foo.c:36:12: error: 'true' undeclared (first use in this function); did you mean 'trunc'?
     flag = true;
            ^~~~
            trunc
foo.c: In function 'main':
foo.c:9:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &x1, &y1);
  ^~~~~~~~~~~~~~~~~~~~~~~~
foo.c:10:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &x2, &y2);
  ^~~~~~~~~~~~~~~~~~~~~~~~

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