A, B, C, D, E = map(int, input().split())
N = A * (B - C)

ans = 0
prev = 1
for i in range(1, N + 1):
    if i == 1:
        ans += D
        prev = D
    else:
        if i % 10 != 0:
            ans += prev
        elif E <= prev:
            ans += prev - E
            prev -= E
        else:
            ans += prev
print(ans)