library(data.table)

clicks_test   <- fread( "../input/clicks_test.csv")
clicks_test[,prob:=ad_id/1e7]

setkey(clicks_test,"prob")
submission <- clicks_test[,.(ad_id=paste(rev(ad_id),collapse=" ")),by=display_id]
setkey(submission,"display_id")

write.csv(submission,file = "submission7.csv",row.names = F)