蓝桥杯入门题

1.
#include <iostream>
#define MAX 1000000
#define a 10007
using namespace std;
int n, i, F[MAX];
int main(){
	while (cin >> n) {
		F[1] = 1;
		F[2] = 1;
		for (i = 3; i <= n; ++i)
			F[i] = (F[i - 1] + F[i - 2]) % a;
		cout << F[n]<<endl;
	}
	return 0;
}
2. 
#include <iostream>
#include <iomanip>
#define PI 3.14159265358979323846
using namespace std;
int main()
{
	int r;
	double s;
	cin >> r;
	s = PI*r*r;
	cout << setiosflags(ios::fixed)<<setprecision(7)<<s;
	//setiosflags(ios::fixed)主要是将流的格式设置为：fixed(将一个浮点表示为一个定点整数和小数点和小数部分的格式。然后setprecision(4)表示小数部分的精度为4位
	return 0;
}
3.
#include <iostream>
using namespace std;
int main()
{
	long long int n,sum;
	while (cin >> n) {
		if (n % 2 == 0) {
			sum = (n / 2)*(1 + n);
			cout << sum << endl;
		}
		else if (n % 2 != 0) {
			sum = (((n - 1) / 2)*n) + n;
			cout << sum << endl;
		}
	}
	return 0;
}
4．
#include <iostream>
using namespace std;
int main(){
    int a, b;
    cin >> a >> b;
    cout << a + b;
    return 0;
}