diff --git a/trees/segtree-d.cc b/trees/segtree-d.cc
index 1c0361c..f087331 100644
--- a/trees/segtree-d.cc
+++ b/trees/segtree-d.cc
@@ -1,6 +1,6 @@
 constexpr int MAXN=1e5+10;
 int cnt,root;
-int d[MAXN*2],ls[MAXN*2],rs[MAXN*2];
+int d[MAXN*2],ls[MAXN*2],rs[MAXN*2];  // minimum size is q*log(N)
 
 void update(int s,int t,int &p,int x,int c){  // add constant c to #x
     if(!p)p=++cnt;  // create node