#include <bits/stdc++.h>
using namespace std;

const int M = 32;
int n;
int x[16]; // x[i] in 1 .. M
int y[16];

int F[M+1];
int f(int x){return F[x] == x ? x : F[x] = f(F[x]);}
bool important[M+1];
int flux[M+1]; // from i to i+1

void merge(int a, int b)
{
	int fa = f(a), fb = f(b);
	if(fa != fb)
		F[fa] = fb;
}

struct edge
{
	int a, b, len;
	bool operator <(const edge that)const
	{
		return len < that.len;
	}
};

int solve()
{
	for(int i = 1; i <= M; i++)
		F[i] = i;
	memset(flux, 0, sizeof(flux));
	memset(important, false, sizeof(important));
	for(int i = 0; i < n; i++)
	{
		merge(x[i], y[i]);
		important[x[i]] = important[y[i]] = true;

		if(x[i] < y[i])
			for(int j = x[i]; j < y[i]; j++)
				flux[j] ++;
		if(x[i] > y[i])
			for(int j = y[i]; j < x[i]; j++)
				flux[j] --;
	}
	int ans = 0;
	for(int i = 1; i < M; i++)
	{
		if(flux[i] < 1)
			merge(i, i+1);
		if(flux[i] > 1)
		{
			ans += flux[i] - 1;
			merge(i, i+1);
		}
	}
	vector <edge> lis;
	int prevImportant = -1;
	for(int i = 1; i <= M; i++)
		if(important[i])
		{
			if(prevImportant != -1)
			{
				if(f(prevImportant) != f(i))
				{
					edge e;
					e.a = prevImportant;
					e.b = i;
					e.len = i - prevImportant;
					lis.push_back(e);
				}
			}
			prevImportant = i;
		}
	sort(lis.begin(), lis.end());
	for(int i = 0; i < lis.size(); i++)
	{
		if(f(lis[i].a) != f(lis[i].b))
		{
			ans += lis[i].len;
			merge(lis[i].a, lis[i].b);
		}
	}
	return ans;
}

int dp[1<<16][16];

int dodp(int mask, int last)
{
	if(mask == (1<<n)-1) return 0;
	int &ret = dp[mask][last];
	if(ret != -1) return ret;
	ret = 1000000000;
	for(int i = 0; i < n; i++)
		if((mask & (1<<i)) == 0)
			ret = min(ret, dodp(mask | (1<<i) , i) + max(0, y[last] - x[i]));
	return ret;
}

int bruteforce()
{
	memset(dp, 0xff, sizeof(dp));
	int ret = 1000000000;
	for(int i = 0; i < n; i++)
		ret = min(ret, dodp(1<<i, i));
	return ret;
}

int MAIN()
{
	srand((unsigned)time(NULL));
	int nCorrect = 0;
	for(int testCase = 1; testCase <= 500; testCase ++)
	{
		/*cin >> n;
		for(int i = 0; i < n; i++)
			cin >> x[i];
		for(int i = 0; i < n; i++)
			cin >> y[i];*/
		n = rand() % 16 + 1;
		for(int i = 0; i < n; i++)
		{
			x[i] = rand() % 32 + 1;
			y[i] = rand() % 32 + 1;
		}
		int ansBF = bruteforce();
		int ans = solve();
		if(ansBF != ans) cout << "ERROR" << endl;
		else nCorrect ++;
	}
	cout << nCorrect << " correct " << endl;
	return 0;
}

int main()
{
	int start = clock();
	#ifdef LOCAL_TEST
		freopen("in.txt", "r", stdin);
		freopen("out.txt", "w", stdout);
	#endif
	ios :: sync_with_stdio(false);
	cout << fixed << setprecision(16);
	int ret = MAIN();
	#ifdef LOCAL_TEST
		cout << "[Finished in " << clock() - start << " ms]" << endl;
	#endif
	return ret;
}