#include <stdio.h>
int n, m, cnt, ans;
inline int f(int n)
{
	cnt = 0;
	while(n)
		cnt += n % 10 == 2, n /= 10;
	return cnt;
}
int main()
{
    scanf("%d %d", &n, &m);
    while(n <= m)
    	ans += f(n ++);
	printf("%d\n", ans);
    return 0;
}