Untitled

#include <iostream>
#include <math.h>
using namespace std;

int main()
{
    setlocale(LC_ALL, "rus");

	int num;
    cout << "Задание ";
	cin >> num;
    
	switch (num)
	{
	case 1: 
		double r, l, s;
		cout << "введите R ";
		cin >> r;
		l = 2 * 3.14 * r;
		s = 3.14 * pow(r, 2);
		cout << l << endl << s << endl;
		break;
	case 2:
		int n2, a, b, c, sum;
		cout << "Введите трёхзначное число ";
		cin >> n2;
		a = n2 % 10;
		b = n2 / 10 % 10;
		c = n2 / 100 % 10;
		sum = a + b + c;
		cout << sum;
		break;
	case 3: 
		int n3, c3;
		cout << "Введите число ";
		cin >> n3;
		c3 = n3 % 10;
		cout << c3;
		break;
	case 4: 
		double a4, b4;
		cout << "Введите a и b ";
		cin >> a4 >> b4;
		a4 = a4 + b4;
		b4 = b4 + a4;
		a4 = b4 - a4;
		b4 = b4 - 2 * a4;
		cout << a4 << endl << b4;
		break;
	case 5:
		double a5, b5, c5;
		cout << "Введите a и b ";
		cin >> a5 >> b5;
		c5 = a5;
		a5 = b5;
		b5 = c5;
		cout << a5 << endl << b5;
		break;
	case 6:
		double s6, m6, n6, a6, b6;
		cout << "Введите S, m, n ";
		cin >> s6 >> m6 >> n6;
		a6 = sqrt(m6 * s6 / n6);
		b6 = s6 / a6;
		cout << a6 << endl << b6;
		break;
	case 7: 
		double n7, s7;
		cout << "Введите n ";
		cin >> n7;
		s7 = pow(2 + 2 * n7, 2) / n7;
		cout << s7;
		break;
	case 8:
		int a8, b8, c8;
		cout << "Введите A1, A2, A3 ";
		cin >> a8 >> b8 >> c8;
		a8 = a8 - b8;
		b8 = 2 * a8;
		c8 = 2 * c8;
		c8 = c8 - a8;
		a8 = 2 * a8;
		cout << a8 << endl << b8 << endl << c8 << endl;
		break;
	case 9: 
		int a9, b9, m9, n9;
		cout << "Введите m и n";
		cin >> m9 >> n9;
		b9 = (n9 - m9) / 4;
		a9 = 3 * (n9 - m9) / 4;
		cout << a9 << endl << b9;
		break;
	case 10:
		double m10, n10, a10, b10, x10;
		cout << "Введите m, n, a, b";
		cin >> m10 >> n10 >> a10 >> b10;
		x10 = (m10 - n10) / (a10 - b10);
		cout << x10;
		break;
	default:
		break;
	}

}