View Code of Problem 27

#include<stdio.h>
#include<math.h>
int main(){
	int a, b, i, j, flag;
	long sum;
	while(~scanf("%d%d",&a, &b)){
		sum = 0;
		if(a > b){
			a = a + b;
			b = a - b;
			a = a - b;
		}
		for(i = a + 1; i < b; i ++){
			flag = 0;
			for(j = 2; j <= sqrt(i); j ++){
				if(i % j == 0){
					flag = 1;
					break;
				}
			}
			if(flag == 0){
				sum += i;
			}
		}
		printf("%ld\n",sum);
	}
	return 0;
}