foo.cc: In function 'void Init()':
foo.cc:44:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d%d%d%d", &N, &m, &S, &T); S--; T--;
 ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:48:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d%d", &u, &v); u--; v--;
 ~~~~~^~~~~~~~~~~~~~~~

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