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#include <bits/stdc++.h>
using namespace std;



        /* ------- declaration ------- */

    long long l, r;
    long long cr, ans;


    long long calc(int n) {
        long long base = 1;
        long long res = 0;
        do {
            if (n&1)
                res += 7*base;
            else
                res += 4*base;
            n >>= 1, base *= 10;
        }
        while (n > 1);
        return res;
    }

/* ------- ~~~~~~~~~~~ ------- */



        /* ----------------- main func ----------------- */

    void query() {
        cin >> l >> r;


        for (int i = 2; true; ++i) {
            cr = calc(i);
            if (cr > r) break;
            if (cr >= l)
                ans += (cr - l + 1)*cr,
                l = cr + 1;
        }
        ans += (r - l + 1)*cr;


        cout << ans;
    }

/* ----------------- ~~~~~~~~~ ----------------- */



int main(){
    //freopen("Test.INP", "r", stdin);
    //freopen("Test.OUT", "w", stdout);
    cin.tie(NULL)->sync_with_stdio(false);

        /* ------- setup ------- */

    srand(time(0));
    cout << fixed << setprecision(2);
    int t = 1; for (; t--; query());

/* ------- ~~~~~ ------- */

    return 0;
}