foo.cc: In function 'int main()':
foo.cc:19:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &n, &m);
   ~~~~~^~~~~~~~~~~~~~~~~
foo.cc:26:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d %d", &tfrom, &tto, &tl);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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