View Code of Problem 3493

#include<stdio.h>
#include<stdbool.h>
#include<math.h>
bool ss(int a){
	if(a<=1)
	return false;
	for(int i=2;i<=sqrt(a);i++)
	if(a%i==0)
	return false;
	return true;
}
int main(){
	int a,b;
	while(scanf("%d %d",&a,&b)!=EOF){
		int count=0;
		if(a==-1&&b==-1)
		break;
		for(int i=a;i<=b;i++)
		if(ss(i))
		count++;
		printf("%d\n",count);
	}
}