#include<stdio.h>
int main() {

	int l = 0, r = 0;
	scanf("%d %d", &l, &r);
	int cnt = 0;//计数
	//把i当作轮次,不然会死循环
	for (int i = l; i <= r; i++) {

		int test = i;
		while (test) {
			//余数而不是除数
			if (test % 10 == 2) {
				cnt++;
			}
			test = test / 10;
		}
	}
	printf("%d\n", cnt);

	return 0;
}