View Compilation Error

0_0_39656810_7677.cpp:1:1: error: expected unqualified-id before 'public'
    1 | public class PrimeExpressionChecker {    public static boolean isPrime(int num) {        if (num < 2) {            return false;        }        for (int i = 2; i * i <= num; i++) {            if (num % i == 0) {                return false;            }        }        return true;    }    public static void checkExpression(int x, int y) {        boolean allPrime = true;        for (int n = x; n <= y; n++) {            int expressionValue = n * n + n + 41;            if (!isPrime(expressionValue)) {                allPrime = false;                break;            }        }        if (allPrime) {            System.out.println("OK");        } else {            System.out.println("Sorry");        }    }    public static void main(String[] args) {        Scanner scanner = new Scanner(System.in);        while (true) {            int x = scanner.nextInt();            int y = scanner.nextInt();            if (x == 0 && y == 0) {                break;            }            checkExpression(x, y);        }    }}
      | ^~~~~~