题目：

https://www.luogu.com.cn/problem/P1179

思路：直接暴力过

代码：

#include<iostream>
using namespace std;
int cnt(int x)
{
	int sum = 0;
	while(x)
	{
		int temp = x %10;
		if(temp == 2)
		{
			sum++;
		}
		x = x/10;
	}
	return sum;
}
int main(void)
{
	int L,R;
	cin >> L >> R;
	int S = 0;
	for(int i = L ; i <= R ; i++)
	{
		S = S + cnt(i);
	}
	cout << S; 
	return 0;
 }