foo.c: In function 'main':
foo.c:26:3: warning: statement with no effect [-Wunused-value]
   for (start; start < end + 1; start++)
   ^~~
foo.c:14:7: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  Koop:scanf("%d%d", &L, &M);
       ^~~~~~~~~~~~~~~~~~~~~
foo.c:21:8: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   Loop:scanf("%d%d", &start, &end);
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~

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