import java.util.Scanner;
public class Main{
public static void main(String[] args){
Scanner scanner = new Scanner(System.in);
int first = scanner.nextInt();
int second = scanner.nextInt();
int sum = 0;
for(int index = first; index <= second; index++){
if(check(index)){
sum += index;
}
}
System.out.print(sum);
}
private static boolean check(int num){
if (num < 2) return false;
for (int index = 2; index <= num / index; index++ )
{
if (num % index == 0) {
return false;
}
}
return true;
}
}

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