// Euclid's GCD by repeated subtraction.

import java.util.*;

public class GCD {
  public static int GCD(int a, int b) {
    while ((a != b)) {
      if ((a > b)) {
        a = (a - b);
      }
      if ((b > a)) {
        b = (b - a);
      }
    }
    return a;
  }

  public static void main(String[] args) {
    int a = 0;
    int b = 0;
    int result = GCD(a, b);
    System.out.println(result);
  }
}