#include <stdio.h>
#include <math.h>

int is_prime(int num) {
	int i;
    if (num <= 1) {
        return 0;
    }
    
    for (i = 2; i <= sqrt(num); i++) {
        if (num % i == 0) {
            return 0;
        }
    }
    
    return 1;
}

int prime_sum(int lower, int upper) {
    int sum = 0;
    int i;
    for (i = lower; i <= upper; i++) {
        if (is_prime(i)) {
            sum += i;
        }
    }
    
    return sum;
}

int main() {
    int lower, upper;
    scanf("%d %d", &lower, &upper); // 输入区间的上下界
    
    int result = prime_sum(lower, upper);
    
    printf("%d-%d之间的素数和是%d\n", lower, upper, result);
    
    return 0;
}