foo.cc: In function 'int main()':
foo.cc:15:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
     ~~~~~^~~~~~~~~~
foo.cc:16:42: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     for ( int i = 1; i <= n; i ++ ) scanf("%d", &a[i]);
                                     ~~~~~^~~~~~~~~~~~~

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