package main

import . "fmt"

func main() {
	var n int
	Scan(&n)
	ts := make([]int, n)
	for i := range ts {
		Scan(&ts[i])
	}
	count := 0
	last := 0
	for _, t := range ts {
		var s int
		Scan(&s)
		if last < s*10 {
			last = (s+t)*10-1
			count++
		}
	}
	Println(count)
}