output_description: If N_1, N_2, N_3 and N_4 can be arranged into the sequence of digits "1974",
  print `YES`; if they cannot, print `NO`.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N_1 N_2 N_3 N_4
attempt: #include <iostream>
  #include <vector>
  #include <algorithm>
  #include <utility>
  #include <string>
  #include <queue>
  #include <stack>
  
  using namespace std;
  
  typedef long long int ll;
  typedef pair<int, int> Pii;
  
  const ll mod = 1000000007;
  
  int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
  
    vector<int> n(4);
    for (auto &x: n) cin >> x;
  
    sort(n.begin(), n.end());
    if (n[0] == 1 && n[1] == 4 && n[2] == 7 && n[3] == 9) {
      cout << "YES" << endl;
    }
    else {
      cout << "NO" << endl;
    }
  
    return 0;
  }
  
problem_description: Statement
  
  You are given four digits N_1, N_2, N_3 and N_4. Determine if these can be
  arranged into the sequence of digits "1974".
samples: [{"input": "1 7 9 4", "output": "YES\n    \n\nWe can get 1974 by swapping N_2 and N_3.\n\n* * *"}, {"input": "1 9 7 4", "output": "YES\n    \n\nWe already have 1974 before doing anything.\n\n* * *"}, {"input": "1 2 9 1", "output": "NO\n    \n\n* * *"}, {"input": "4 9 0 8", "output": "NO"}]