foo.c: In function 'main':
foo.c:14:2: warning: statement with no effect [-Wunused-value]
  for (t; --t; t >= 0) {
  ^~~
foo.c:14:17: warning: statement with no effect [-Wunused-value]
  for (t; --t; t >= 0) {
               ~~^~~~
foo.c:5:19: warning: unused variable 'p' [-Wunused-variable]
  int a, q = 1, c, p = 0;
                   ^
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &a);
  ^~~~~~~~~~~~~~~

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