foo.cc: In function 'int main()':
foo.cc:24:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lld", &n);
     ~~~~~^~~~~~~~~~~~
foo.cc:26:59: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%lld", &a[i]), rt[i][i] = i, f[i][i] = a[i], f[i][i - 1] = 1;
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~

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