#E366. 【提高】Pell数列

    Type: Default 1000ms 16MiB

【提高】Pell数列

You cannot submit for this problem because the contest is ended. You can click "Open in Problem Set" to view this problem in normal mode.

说明

有一种数列,它的前10项的值分别为:1 2 5 12 29 70 169 408 985 2378,这个数列被称为Pell数列,请问该数列的第n项的值是多少?(n<=1000

输入格式

一个整数n

输出格式

n项的值

样例

10
2378

测验

Not Attended
Status
Done
Rule
IOI
Problem
4
Start at
2022-8-16 19:30
End at
2022-8-16 21:30
Duration
2 hour(s)
Host
Partic.
2