foo.cc: In function 'int main()':
foo.cc:72:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d", &n, &m, &s);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~
foo.cc:78:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d%d", &u, &v, &w);
         ~~~~~^~~~~~~~~~~~~~~~~~~~~~

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