a, b, c, d, e = list(map(int, input().split()))
come = b - c
buy = come * a
sum = 0

if come != 0:
    x = 0
    for i in range(buy):
        res = 0
        if i == 0:
            res = d
        else:
            if i % 10 != 0:
                res = x
            elif i % 10 == 0 and e <= x:
                res = x - e
            elif i % 10 == 0 and e >= x:
                res = x

        x = res
        sum += res
            
print(sum)