fun main() {
    val (a,b,c,d,e) = readLine()!!.split(" ").map{it.toInt()}
    println(if(b == c){
        0
    }else{
        var answer = d
        var bef = d
        for(i in 2..a*(b-c)){
            if(i%10 == 0 && e <= bef)   bef -= e
            answer += bef
        }
        answer
    })
}