func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     queue<unsigned long long> q;     vector<unsigned long long> v;     unsigned long long temp;     q.push(0);     while (!q.empty()) {       temp = q.front();       v.push_back(temp * 10 + 4);       v.push_back(temp * 10 + 7);       if (temp * 10 + 7 >= 4444444444) break;       q.pop();       q.push(temp * 10 + 4);       q.push(temp * 10 + 7);     }     unsigned long long left, right, sum = 0;     cin >> left >> right;     int i = 0;     for (i = 0; i < v.size(); i++)       if (v[i] >= left) break;     while (left <= right) {       sum = sum + v[i] * (min(v[i], right) - left + 1);       left = v[i] + 1;       i++;     }     cout << sum;     return 0;   }   