import java.util.Scanner;

public class Main { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); int start = scanner.nextInt(); int end = scanner.nextInt(); method(start,end); }

public static boolean isPrim(int number){
    if(number <= 2 || number % 2 == 0){
        return false;
    }
    for(int i = 3;i <= Math.sqrt(number);i+=2){
        if(number % i == 0){
            return false;
        }
    }
    return true;
} 
    
public static void method(int start, int end) {
    int count=0;

    //write your code here......
    int temp = 0;
    if(start > end){
        temp = start;
        start = end;
        end = temp;
    }
    
    for(int i = start;i <= end;i++){
        if(isPrim(i)){
            count++;
        }
    }
    System.out.println(start+"到"+end+"之间有"+count+"个大于2的素数");
}

}