查找从1到20的lcm，给出错误"at Main.gcd(Main.java:21)“

public class Main {
    public static void main(String[] args) {
        long lcm = calculateLCM(1, 20);
        System.out.println("LCM of 1 to 20 is: " + lcm);
    }
    
    public static long calculateLCM(int start, int end) {
        long lcm = start;
        
        for (int i = start + 1; i <= end; i++) {
            lcm = calculateLCM(lcm, i);
        }
        
        return lcm;
    }
    
    public static long calculateLCM(long a, long b) {
        long gcd = calculateGCD(a, b);
        return (a * b) / gcd;
    }
    
    public static long calculateGCD(long a, long b) {
        if (b == 0) {
            return a;
        }
        
        return calculateGCD(b, a % b);
    }
}