taxi.c

#include <stdio.h>
int main(){
	int limit,a,b,ans,j,i,four,temp;
	int x[100], d[100];
	scanf("%d",&limit);
	for (a=0;a<limit;a++){
		scanf("%d",&x[a]);
	}
	for(a=0;a<limit;a++){
		for(b=0;b<limit-a;b++){
			if(x[b]<x[b+1]){
				temp=x[b+1];
				x[b+1]=x[b];
				x[b]=temp;
			}
		}
	}
	ans = 0;
	j = limit-1;
	i = 0;
	while (i<=j){
		ans+=1;
		four = 4-x[j];
		while(x[j]<=four && j>=i){
			four =four -  x[j];
			j--;
		}
		i++;
	}
	printf("%d",ans);
}