fun main(args: Array<String>) {
    val (a,b,c,d,e) = readLine()!!.split(" ").map { it.toInt() }
    val candyCount = (b-c)*a
    val candy = mutableListOf<Int>()
    if(candyCount > 0) {
        candy.add(d)
        for(i in (2..candyCount)) {
            if(i % 10 == 0) {
                candy.add(candy.last())
            } else if(e <= candy.last()) {
                candy.add(candy.last() - e)
            } else {
                candy.add(candy.last())
            }
        }
    }
    println(candy.sum())
}