package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)

	var a, b, c, d, e int
	scanner.Scan()
	a, _ = strconv.Atoi(scanner.Text())
	scanner.Scan()
	b, _ = strconv.Atoi(scanner.Text())
	scanner.Scan()
	c, _ = strconv.Atoi(scanner.Text())
	scanner.Scan()
	d, _ = strconv.Atoi(scanner.Text())
	scanner.Scan()
	e, _ = strconv.Atoi(scanner.Text())

	ans := 0
	tmp := d
	for i := 1; i <= a*(b-c); i++ {
		if i%10 == 0 && e <= tmp {
			tmp -= e
		}
		ans += tmp
	}
	fmt.Println(ans)
}