package main

import . "fmt"

func main() {
	var n int
	Scan(&n)
	var k int64 = 1
	for i := 0; i < n; i++ {
		var p int64
		Scan(&p)
		k *= p
		for k >= 10 {
			k = k / 10 + k % 10
		}
	}
	Println(k)
}