import java.util.Scanner;
public class Main{
static long F[] = new long[91];
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
F[1] = 1;
F[2] = 2;
for (int i = 3; i <= 90; i++) {
F[i] = F[i-1] + F[i-2];
}
while( scanner.hasNext() ){
int n = scanner.nextInt();
System.out.println(F[n]);
}
}
}
/**************************************************************
Problem: 1205
User: yihukurama
Language: Java
Result: Accepted
Time:120 ms
Memory:18836 kb
****************************************************************/