using System;

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public class Program

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{

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public static void Main()

{

            //1.khai bao bien,nhap ban kinh

            Console.Write("nhap ban kinh r:");

            int r = Convert.ToInt32(Console.ReadLine());

            double pi = 3.14;

            //2.tinh chuvi,dientich;

            double chuvi, dientich;

            chuvi =2*r*pi;

            dientich = r * r * pi;

            //3.xuat ketqua

            Console.Write("\nchuvila:{0}",chuvi);

            Console.Write("\ndientichla:{0}", dientich);

}

}

​

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​