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>

int main(){
        int N,count=0,i=1;
        int f[90];
        f[0] = 2;
        f[1] = 1;
        scanf("%d",&N);
        if (N==0){
                printf("2");
        }
        if(N==1){
                printf("1");
        }

        while(i<=N){
                count=count +1;
                i = i+1;
                f[i] = f[i-1]+f[i-2];
        }
        if(N>=2){
                printf("%d\n",f[i-1]);
        }

        return 0;
}