func_code_string: #include <bits/stdc++.h>   using namespace std;   int arr[10000];   int n = 0;   void init() {     queue<string> q;     q.push( 4 );     q.push( 7 );     while (!q.empty()) {       string u = q.front();       q.pop();       arr[n++] = stoi(u);       if (u.length() < 9) {         q.push(u +  4 );         q.push(u +  7 );       }     }   }   int main() {     ios_base::sync_with_stdio(false);     init();     int t = 1;     while (t--) {       int k;       cin >> k;       cout << lower_bound(arr, arr + n, k) - arr + 1 << endl;     }     return 0;   }   