Превоз

#include <iostream>

using namespace std;

int main()
{
    int n,temp,sum=0,taxis=0,capacity=0;
    cin>>n;
    int kids[4]={0,0,0,0};
    for(int j=0;j<n;j++)
    {
        cin>>temp;
        kids[temp-1]++;
        sum++;
    }
    while(sum>0)
    {
        taxis++;
        capacity=4;
        if(kids[3]>0)
        {
            kids[3]--;
            sum--;
        }
        else
        {
            if(kids[2]>0)
            {
                kids[2]--;
                sum--;
                capacity-=3;
            }
            if(kids[1]>0 && capacity>=2)
            {
                if(kids[1]>1 && capacity==4)
                {
                    kids[1]-=2;
                    sum-=2;
                    capacity=0;
                }
                else
                {
                    kids[1]--;
                    sum--;
                    capacity-=2;
                }
            }
            if(kids[0]>0 && capacity>=1)
            {
                if(capacity==4 && kids[0]>=4)
                {
                    kids[0]-=4;
                    sum-=4;
                }
                else if(capacity>=3 && kids[0]>=3)
                {
                    kids[0]-=3;
                    sum-=3;
                }
                else if(capacity>=2 && kids[0]>=2)
                {
                    kids[0]-=2;
                    sum-=2;
                }
                else
                {
                    kids[0]--;
                    sum--;
                }
            }
        }
    }
    cout<<taxis<<endl;
    return 0;
}