C++ :

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

#define MAXNUM (777777777)
#define MAXN (100000 + 5)

int T;
int a, b;

long long _p[MAXN];
int _p_c;

long long ans;

void dfs(long long s) {
    if (s > MAXNUM) return ;

    _p[_p_c++] = s;

    dfs (1LL * s * 10 + 4);
    dfs (1LL * s * 10 + 7);
}


void init () {
    memset(_p, 0, sizeof(_p));
    _p_c = 0;
    dfs(0);
    _p[_p_c] = 4444444444LL;
    sort(_p, _p + _p_c);
//    for (int i=0; i<_p_c; i++) {
//        printf ("%d ", _p[i]);
//    }
//    printf("\n_p_c: %d\n", _p_c);
}

int main () {

//    freopen("B.in", "r", stdin);
    init();
//    cout << lower_bound(_p, _p + _p_c, 74) - _p <<endl;

    scanf ("%d", &T);
    while (T--) {
        scanf("%d %d", &a, &b);

        int l = lower_bound(_p, _p + _p_c, a) - _p;
        int r = lower_bound(_p, _p + _p_c, b) - _p;

//        cout << l << " " << r << endl;

        ans = 0;

        if (a <= _p[l]) {
            ans += (long long)1 * _p[l] * (_p[l] - a + 1);
        }

//        cout << ans << endl;
        for (int i=l; i<r; i++) {
            ans += (long long)1 * _p[i+1] * (_p[i+1] - _p[i]);
        }

//        cout << ans << endl;
//
        if (_p[r] > b) {
            ans -= (long long)1 * _p[r] * (_p[r] - b);
//            cout << _p[r] << " " << (b - _p[r-1]) << endl;
        }
        cout << ans << endl;
    }
}