View Code of Problem 27

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