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  1. #include<iostream>
  2. using namespace std;
  3. int main()
  4. {
  5.     long long int n;
  6.     int x=0,count=0,c4=0,c3=0,c2=0,c1=0;
  7.     cin>>n;
  8.     while(n--)
  9.     {
  10.         cin>>x;
  11.         if(x==4)
  12.             c4++;
  13.         else if(x==3)
  14.             c3++;
  15.         else if(x==2)
  16.             c2++;
  17.         else if(x==1)
  18.             c1++;
  19.     }
  20.  
  21. //    cout<<c4<<" "<<c3<<" "<<c2<<" "<<c1<<endl;
  22.     count+=c4;
  23.     c4=0;
  24.     if(c3>=c1)
  25.     {
  26.         count+=c3;
  27.         c3=c1=0;
  28.     }
  29.     else
  30.     {
  31.         count+=c3;
  32.         c1-=c3;
  33.         c3=0;
  34.     }
  35.     if(c2>=c1)
  36.     {
  37.         if(c1%2==0)
  38.         {
  39.             c1/=2;
  40.             count+=c1;
  41.             c2-=c1;
  42.         }
  43.         else
  44.         {
  45.             c1+=1;
  46.             c1/=2;
  47.             count+=c1;
  48.             c2-=c1;
  49.         }
  50.         if(c2>=2)c2/=2;
  51.         count+=c2;
  52.     }
  53.     else
  54.     {
  55.         if(c1%2==0)
  56.         {
  57.             c1/=2;
  58.             count+=c2;
  59.             c1-=c2;
  60.         }
  61.         else
  62.         {
  63.             c1+=1;
  64.             c1/=2;
  65.             count+=c2;
  66.             c1-=c2;
  67.         }
  68.         if(c1>=2)c1/=2;
  69.         count+=c1;
  70.     }
  71.     cout<<count<<endl;
  72.     return 0;
  73. }
  74.  
Success #stdin #stdout 0s 3472KB
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https://ideone.com/cTEsEx
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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