foo.c: In function 'main':
foo.c:18:16: error: 'x' undeclared (first use in this function)
   18 |    t=prime(t,a[x]);
      |                ^
foo.c:18:16: note: each undeclared identifier is reported only once for each function it appears in
foo.c:13:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   13 |    scanf("%d",&n);
      |    ^~~~~~~~~~~~~~
foo.c:15:6: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   15 |      scanf("%d",&a[i]);
      |      ^~~~~~~~~~~~~~~~~

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