foo.cc: In function 'bool cmp(node, node)':
foo.cc:17:27: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
 { return a.a<b.a||a.a==b.a&&a.b<b.b;}
                   ~~~~~~~~^~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:57:18: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   while(j<=q[i].x&&j<k||i==cnt)
         ~~~~~~~~~^~~~~
foo.cc:42:9: warning: unused variable 'x' [-Wunused-variable]
  double x;
         ^

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