foo.cc: In function 'void build(int, int, int)':
foo.cc:57:11: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   57 |  int mid=l+r>>1;
      |          ~^~
foo.cc: In function 'void modify(int, int, int, int)':
foo.cc:73:17: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   73 |  int mid=tr[u].l+tr[u].r>>1;
      |          ~~~~~~~^~~~~~~~

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