func_code_string: #include <bits/stdc++.h>   using namespace std;   string vow =  aeiou ;   const int dxhorse[] = {-2, -2, -1, -1, 1, 1, 2, 2};   const int dyhorse[] = {1, -1, 2, -2, 2, -2, 1, -1};   const int dx[] = {-1, 0, 0, 1};   const int dy[] = {0, -1, 1, 0};   const long double pie = 3.14159265358979;   const long long mod = 1e9 + 7;   long long ans = LLONG_MAX;   long long in;   void f(long long n, int four, int sev) {     if (n > 1e11) return;     if (n >= in) {       if (four == sev) ans = min(ans, n);     }     f(n * 10 + 4, four + 1, sev);     f(n * 10 + 7, four, sev + 1);   }   void solve(int test_case) {     cin >> in;     f(0, 0, 0);     cout << ans;   }   int main() {     int t = 1;     for (int i = 0; i < t; i++) solve(i);     return 0;   }   