60pts 求调

#include<iostream>
using namespace std;
#define int long long
int climbStairs(int n) {
    if (n == 1) return 1;
    if (n == 2) return 2;
    int dp1 = 1, dp2 = 2;
    for (int i = 3; i <= n; i++) {
        int temp = dp2;
        dp2 = dp1 + temp;
        dp1 = temp;
    }
    return dp2;
}
int n;
signed main() {
    cin >> n;
    cout << climbStairs(n) << endl;
    return 0;
}