a,b,c,d,e = map(int,input().split())
ans = 0
x = 0
for i in range(1,(b-c)*a +1):
    if i == 1:
        ans += d
        x = d
        continue
    if i % 10 != 0:
        ans += x
        continue
    if i % 10 == 0 and e <= x:
        ans += x-e
        x = x-e
        continue
    if i % 10 == 0 and e > x:
        ans += x
        continue
print(ans)