foo.c: In function 'main':
foo.c:9:11: error: 'L' undeclared (first use in this function)
  for (j = L - 1; j < R + 1; j++) {
           ^
foo.c:9:11: note: each undeclared identifier is reported only once for each function it appears in
foo.c:9:22: error: 'R' undeclared (first use in this function)
  for (j = L - 1; j < R + 1; j++) {
                      ^
foo.c:8:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d",&l,&r);
  ^~~~~~~~~~~~~~~~~~~~

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