public class Main {
public static void main(String[] args) {
int n = 44;
int result = climbStairs(n);
System.out.println(result);
}
public static int climbStairs(int n) {
if (n <= 3 && n>0) {
return n;
}
if (n <= 0) {
return -1;
}
int[] Dp = new int[n+1];
Dp[1] = 1;
Dp[2] = 2;
for (int i = 3; i <= n; i++) {
Dp[i] = Dp[i - 1] + Dp[i - 2];
}
return Dp[n];
}
}