func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     char no[20];     cin >> no;     int len = strlen(no);     int ans = (1 << len) - 2;     for (int i = (len - 1), pos = 0; i >= 0; i--, pos++) {       if (no[i] ==  7 ) ans += (1 << pos);     }     cout << ans + 1 << endl;     return 0;   }   