Problem:
Score : 200 points

Problem Statement

It is November 18 now in Japan. By the way, 11 and 18 are adjacent Lucas numbers.

You are given an integer N. Find the N-th Lucas number.

Here, the i-th Lucas number L_i is defined as follows:

L_0=2

L_1=1

L_i=L_{i-1}+L_{i-2} (i≥2)

Constraints

1≤N≤86

It is guaranteed that the answer is less than 10^{18}.

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the N-th Lucas number.

Sample Input 1

5

Sample Output 1

11

L_0=2

L_1=1

L_2=L_0+L_1=3

L_3=L_1+L_2=4

L_4=L_2+L_3=7

L_5=L_3+L_4=11

Thus, the 5-th Lucas number is 11.

Sample Input 2

86

Sample Output 2

939587134549734843

Solution in C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>

int main() {

    int n;
    scanf("%d", &n);

    long l0 = 2;
    long l1 = 1;

    int cnt = 3;
    long temp;
    if (n == 1) {
        printf("%ld", l0) ;
    } else if (n == 2) {
        printf("%ld", l1);
    } else {

        while (cnt <= n) {

            temp = l0 + l1;
            l0 = l1;
            l1 = temp;

            cnt++;
        }
        printf("%ld", l0 + l1);
    }

    



    return 0;
}