// No.1453 手助け
package main

import "fmt"

func main() {
	var a, b, c, d, e int
	fmt.Scan(&a, &b, &c, &d, &e)

	n := (b - c) * a
	ans := 0
	for i := 1; i <= n; i++ {
		ans += max(d-e*(i/10), d%e)
	}
	fmt.Println(ans)
}