A,B,C,D,E = map(int,input().split())
if B-C == 0:
    print(0)
    exit()
B -= C
candy = A * B
ans = 0
for i in range(candy):
    if i+1 == 1:
        ans += D
    else:
        if (i+1)%10 == 0:
            if E <= D:
                ans += (D - E)
                D -= E
            else:
                ans += D
        else:
            ans += D
print(ans)