foo.cc: In function 'int main()':
foo.cc:19:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld", &n);
  ~~~~~^~~~~~~~~~~~
foo.cc:20:65: 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("%lld", &f[i][i]),f[i][i-1]=1, root[i][i] = i;
                              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~

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