foo.c: In function 'main':
foo.c:14:14: error: 'true' undeclared (first use in this function)
  for (i = a; true; i++)
              ^~~~
foo.c:14:14: note: each undeclared identifier is reported only once for each function it appears in
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ^~~~~~~~~~~~~~~
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &a, &b);
  ^~~~~~~~~~~~~~~~~~~~~
foo.c:22:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &x);
   ^~~~~~~~~~~~~~~

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