View Code of Problem 3493

#include<iostream>
#include<string>
#include<cmath>
#include<cstring>
#include<vector>
#include<iomanip>
#include<cstdio>
#include<algorithm>
#include<ctype.h>
using namespace std;
int sh(int n)
{
	if (n == 1 || n == 0)
		return 0;
	if (n == 2)
		return 1;
	for (int i = 2;i < (int)sqrt(n) + 1;i++)
	{
		if (n%i == 0)
			return 0;
	}
	return 1;
}
int main()
{
	int a, b;
	while (cin >> a >> b)
	{
		if (a > b)
			swap(a, b);
		int cnt = 0;
		if (a == -1 && b == -1)
		{
			break;
		}
		for (int i = a;i <= b;i++)
		{
			if (sh(i) == 1)
			{
				cnt++;
			}
		}
		cout << cnt << endl;
	}
}