i tried to solve this problem but i have WA 19 , many trials without result so i hope some one can help me <3
my solutin idea :
for each u we preprocess it that we store for it the 1<<k elemnt after u in valid sequence dp[u][k] and sum untill this elemnt sum[u][k] >> so we can ans queryies about u in log time
submission : 268374991