2.1.3 Sorting a Three-Valued Sequence

/*
ID: awsd1231
PROG: sort3 
LANG: C++
*/
#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
int n, a[1010];
int main () {
	freopen("sort3.in", "r", stdin);
    freopen("sort3.out", "w", stdout);
	scanf("%d", &n);
	int c1(0);
	for (int i = 0; i != n; ++i) {
		scanf("%d", &a[i]);
		if(a[i] == 1) ++c1;
	}
	int cnt(0);
	for (int m = 1; m != 3; ++m) {
		for (int i = n - 1; i != -1; --i) {
			bool c3 = false;
			if (a[i] == m) {
				int t = i;
				if (m == 1) t = c1;
				for (int j = 0; j != t; ++j) {
					if (a[j] == 3) {
						int t = a[i];
						a[i] = a[j];
						a[j] = t;
						++cnt;
						c3 = true;
						break;
					}
				}
				if (!c3 && m != 2) {
					for (int j = 0; j != i; ++j) {
						if (a[j] == 2) {
							int t = a[i];
							a[i] = a[j];
							a[j] = t;
							++cnt;
							break;
						}
					}
				}
			}
		}
	}
	cout << cnt << endl;
	return 0;
}