Task

In the city, a bus named Fibonacci runs on the road every day.

There are n stations on the route. The Bus runs from station₁ to station_n.

At the departure station(station₁), k passengers get on the bus.

At the second station(station₂), a certain number of passengers get on and the same number get off. There are still k passengers on the bus.

From station₃ to station_n-1, the number of boarding and alighting passengers follows the following rule:

• At station_i, the number of people getting on is the sum of the number of people getting on at the two previous stations(station_i-1 and station_i-2)
• The number of people getting off is equal to the number of people getting on at the previous station(station_i-1).

At station_n, all the passengers get off the bus.

Now, The numbers we know are: k passengers get on the bus at station₁, n stations in total, m passengers get off the bus at station_n.

We want to know: How many passengers on the bus when the bus runs out station_x.

Input

• k: The number of passengers get on the bus at station₁.

  • 1 <= k <= 100

• n: The total number of stations(1-based).

  • 6 <= n <= 30

• m: The number of passengers get off the bus at station_n.

  • 1 <= m <= 10^10

• x: Station_x(1-based). The station we need to calculate.

  • 3 <= m <= n-1

• All inputs are valid integers.

Output

An integer. The number of passengers on the bus when the bus runs out station_x.