#include <stdio.h>
int Date(int x, int y) {
    int i = 0;
    int count = 0;
    for (i = x; i <= y; i++) {
        int m = i;
        while (m) {
            if (m % 10 == 2) {
                count++;
            }
            m /= 10;
        }
    }
    return count;
}

int main() {
    int L, R;
    scanf("%d %d", &L, &R);
    int ret = Date(L, R);
    printf("%d", ret);
    return 0;
}