foo.cc: In function 'int main(int, const char**)':
foo.cc:67:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
     ~~~~~^~~~~~~~~~
foo.cc:70:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%lf", mat[i] + j);
             ~~~~~^~~~~~~~~~~~~~~~~~~

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