题解 | #斐波那契数列#

public class Program {
    public static void Main() {
        string line;
        while ((line = System.Console.ReadLine ()) != null) { // 注意 while 处理多个 case
            if(!int.TryParse(line, out int n))
                  break;
            var sum = 0;
            if(n == 1 || n == 2)
               sum = 1;
            var sum1 = 1;
            var sum2 = 1;
            while(n > 2)
            {
                sum = sum1 + sum2;
                sum1 = sum2;
                sum2 = sum;
                --n;
            }
            System.Console.WriteLine(sum);
        }
    }
}