4
class Fbo{
public static void main(String[]args){
System.out.println(fn(40));
System.out.println(fn1(40));
}
public static long fn(int n){
if(n<1)return -1;
int x=1;
int y=1;
int sum=0;
for(int i=0;i<n-2;i++){
sum=x+y;
x=y;
y=sum;
}
return sum;
}