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  1.  
  2. #include <bits/stdc++.h>
  3. using namespace std;
  4. #define ll long long
  5. #define endl '\n'
  6. ll N = 1e9+7;
  7. ll oo =1e13;
  8. const ll maxx = 1000000 + 3;
  9. ll n,m,k,q,x,y,z,l,r,mid,ans;
  10.  
  11. void go(ll num){
  12.     //4 ,7 ,44,47,74,77
  13. }
  14. void solve() {
  15.     cin>>n;
  16.  
  17.     ll j=0;
  18.     vector<ll>v={4,7};
  19.     for (ll i =0;i<10;i++) {
  20.         for (;j<v.size();j++) {
  21.             if (v[j]>1e9)break;
  22.             v.push_back(v[j]*10+4);
  23.             v.push_back(v[j]*10+7);
  24.         }
  25.     }
  26.     vector<ll>v2;
  27.     for (ll i =0;i <v.size();i++) {
  28.         ll num=v[i];
  29.         ll f=0,s=0;
  30.         while (num>0) {
  31.             if (num%10==4)f++;
  32.             else s++;
  33.             num/=10;
  34.         }
  35.         if (f==s) v2.push_back(v[i]);
  36.     }
  37.     cout<<*lower_bound(v2.begin(),v2.end(),n);
  38. }
  39. int main() {
  40.     ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
  41.     ll t=1 ;
  42.     // cin >>t;
  43.     while (t--) {
  44.         ans=0;
  45.         solve();
  46.     }
  47. }
Success #stdin #stdout 0.01s 5316KB
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https://ideone.com/Rzl17q
language:
C++ (gcc 8.3)
created:
6 hours ago
visibility:
public

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