public class G4 {
public static void main(String[] args) {
// TODO Auto-generated method stub
int [][] h=new int[39][2];
h[0][0]=1;
h[0][1]=0;
h[1][0]=1;
h[1][1]=1;
for (int i =2; i <39; i++) {
h[i][1]=h[i-2][0]+h[i-1][0];
h[i][0]=h[i-2][1]+h[i-1][1];
}
System.out.print(h[38][1]);
}
}