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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

function main(input) {
  input=input.trim();
  const n = parseInt(input.split(" ")[0], 10);
  if(n==1){
    console.log(2);
  }else if(n==2){
    console.log(1);
  }else{
    var deff=[2,1]
    for(var i=2; i<=n; i++){
      deff.push(deff[i-1]+deff[i-2])
    }
    console.log(deff[n]);
  }

}



main(require('fs').readFileSync('/dev/stdin', 'utf8'));