View Code of Problem 103

#include<stdio.h>
#include<math.h>
int isrish(int n){
	if(n<2) return 0;
	int i;
	for(i = 2;i <= sqrt(n); i++){
		if(n%i==0) return 0;
	}
	return 1;
}
int main(){
	int i,a,b,sum,x[10000];
	sum=0;
	for(i=0;i<10000;i++){
		if(isrish(i)) sum++;
		x[i] = sum;
	}
	while(scanf("%d%d",&a,&b)!=EOF)
	{
		if(x[a]>x[a-1]){
			printf("%d\n",x[b]-x[a]+1);
		}
		else printf("%d\n",x[b]-x[a]);
	}
	return 0;
}