foo.c: In function 'main':
foo.c:4:25: error: expected expression before ';' token
    4 | int n,a[20000],b[20000]=;
      |                         ^
foo.c:5:1: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    5 | scanf("%d",&n);
      | ^~~~~~~~~~~~~~
foo.c:6:22: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    6 | for(int i=1;i<=n;i++)scanf("%d",&a[i]);
      |                      ^~~~~~~~~~~~~~~~~

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