foo.cc: In function 'int main()':
foo.cc:58:8: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   mid=l+r>>1;
       ~^~
foo.cc:44:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~
foo.cc:47:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d%d", &u, &v, w+i);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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