Water Bill

The area where JOI lives has two water companies, company X and company Y. Each company sets the monthly bill from the amount of water used.

• Company X: $A$ yen per liter.
• Company Y: the base fee is $B$ yen. If the usage is at most $C$ liters, only the base fee is charged. If the usage is more than $C$ liters, an extra fee is added to the base fee of $B$ yen: $D$ yen for each liter above $C$.

JOI's house uses $P$ liters of water in a month.

JOI picks the company that makes the bill as cheap as possible. Find the monthly water bill of JOI's house.

The input has 5 lines, one integer per line.

• The first line has $A$, the per-liter charge of company X.
• The second line has $B$, the base fee of company Y.
• The third line has $C$, the usage limit up to which company Y charges only the base fee.
• The fourth line has $D$, the per-liter extra fee of company Y.
• The fifth line has $P$, the amount of water JOI's house uses in a month.

$A$, $B$, $C$, $D$, and $P$ are integers between 1 and 10000, inclusive.

Print the monthly water bill of JOI's house on the first line.

In the first example the usage is 10 liters.

• The bill of company X is $9 \times 10 = 90$ yen.
• The usage is at most 20 liters, so the bill of company Y is the base fee, 100 yen.

Company X is cheaper, so the answer is 90 yen.

In the second example the usage is 250 liters.

• The bill of company X is $8 \times 250 = 2000$ yen.
• The usage is above 100 liters, so the excess is $250 - 100 = 150$ liters. The bill of company Y is the base fee of 300 yen plus an extra fee of $10 \times 150 = 1500$ yen, which is $300 + 1500 = 1800$ yen.

Company Y is cheaper, so the answer is 1800 yen.