題目連結：http://lx.lanqiao.cn/problemset.page?code=BEGIN-&userid=355696

BEGIN-1 A+B問題

#include <bits/stdc++.h>
using namespace std;
int main() {
    int a, b;
    cin >> a >> b;
    cout << a + b << "\n";
    return 0;
}

BEGIN-2 序列求和

#include <bits/stdc++.h>
using namespace
 
 std;
int main() {
    long long n;
    cin >> n;
    cout << n * (n + 1) / 2 << "\n";
    return 0;
}

BEGIN-3 圓的面積

#include <bits/stdc++.h>
using namespace std;
const double PI = acos(-1);
int main() {
    int r;
    cin >> r;
    printf("%.7f", PI * r * r);
    return 0
 
;
}

BEGIN-4 Fibonacci數列

#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 100;
const int MOD = 10007;
int main() {
    vector<int> f(N);
    f[1] = f[2] = 1;
    for (int i = 3; i < N; i++) {
        f[i] = (f[i - 1] + f[i - 2]) % MOD;
    }
    int n;
    cin >> n;
    cout 
 
<< f[n] << "\n";
    return 0;
}