View Code of Problem 27

#include <stdio.h>
#include <string.h> 
#include <math.h>
int main ()
{
	long a,b,i,j;
	long long sum;
	int flag;
	while(scanf("%ld %ld",&a,&b)!=EOF){
		sum=0;
		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&&i!=1){
				sum+=i;
			}
		}
		printf("%lld\n",sum);
	}
	return 0;
}