#include <cstdio>
    #include <iostream>

    using namespace std;

    typedef long long int64;

    int64 new_lucky(int64 a, int64 n) {
      int64 ans = 0;
      int64 cur = 1;
      do {
        if (a % 2) {
          ans += 7 * cur;
        } else {
          ans += 4 * cur;
        }
        a /= 2;
        cur *= 10;
        n--;
      } while (n);
      return ans;
    }

    int main() {
      int a, b;
      scanf("%d%d", &a, &b);
      int64 ans = 0;
      int64 c = 0, d = 1, e = 2;
      int64 cur = -1;
      for ( ; ; ) {
        int64 g = new_lucky(c, d);
        c++;
        if (c == e) {
          c = 0;
          d++;
          e *= 2;
        }
        if (g >= a) {
          if (g >= b) {
            ans += g * (cur == -1 ? b - a + 1 : b - cur);
            break;
          } else {
            ans += g * (cur == -1 ? g - a + 1 : g - cur);
            cur = g;
          }
        }
      }
      cout << ans << endl;
      return 0;
    }