using System;

using System.Collections.Generic;

using System.Linq;

public class Program {

  static int GCD(int a, int b) {

    a = Math.Abs(a);

    b = Math.Abs(b);

​

    if (a == 0)

        return b;

    if (b == 0)

        return a;

​

    if (a % b == 0)

      return b;

​

    return GCD(b, a % b);    

  }

  static int GCD(IEnumerable<int> numbers) {

    if (numbers is null)

      throw new ArgumentNullException(nameof(numbers));

​

    int result = 0;

​

    foreach (var number in numbers) 

      if (result == 0)

        result = number;

      else 

        result = GCD(result, number); 

    return result != 0

      ? result

      : throw new ArgumentOutOfRangeException(nameof(numbers), "Empty sequence");

  } 

  public static void Main() {

    string input = "60 125 2020";

    int gcd = GCD(input

      .Split(' ', StringSplitOptions.RemoveEmptyEntries)

      .Select(item => int.Parse(item)));

​

    Console.Write(gcd);

  }

}