Sections > Recursion > problem:

50723 - Tribonacci

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Section problems

• 50723 - Tribonacci
• 50370 - Number of rectangles in a ...
• 50475 - Voice advertising
• 50909 - Gold Coins
• 50376 - Sequences
• 50725 - Fibonacci Series
• 50385 - The 3n + 1 problem
• 50911 - Symmetric Array
• 50381 - Sum of the numbers

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Time limit 2000/4000/4000/4000 ms. Memory limit 65000/65000/65000/65000 Kb.

Tribonacci

Montenegro Informatics Olympiads 2013

Question:
Tribonacci sequence is obtained by the following formula:


    T_n = T_n-1 + T_n-2 + T_n-3

for a given N and three first elements of the sequence, the formula computes the N-th element of the Tribonacci. Write a program that gets four integers T₁, T₂, T₃ and N. Then the program computes N-th element of the sequence.

Input specification
The input has only one line consisting of 4 integers T₁, T₂, T₃ and N separated by a space where 1 ≤ N ≤ 20 and -20000 ≤ (T₁, T₂, T₃) ≤ 20000.

Output specification
Print the N-th element of the sequence.

Sample Input I `2 3 4 5`	Sample Input II `1 1 1 6`
Sample Output I `16`	Sample Output II `9`

Для отправки решений необходимо выполнить вход.