#include<bits/stdc++.h>

using namespace std;

#define ff first
#define ss second
#define pb push_back
#define mp make_pair

typedef long long ll;
typedef double lf;
typedef pair<int,int> pii;

int main()
{
	cin.tie( NULL );
	ios_base::sync_with_stdio( 0 );

	int n;
	cin >> n;

	vector< int > arr( n );
	for( auto &x : arr )
		cin >> x;

	vector< int > d ( n + 1 );
	d[0] = arr[0];
	for( int i = 1; i < n; ++ i )
		d[i] = arr[i] - arr[i-1];
	d[n] = -arr[n-1];

	vector< int > rd;
	vector< bool > act( n + 1, true );

	int g0 = 0;
	for( int i = 0; i <= n; ++ i )
	{
		if( act[i] == false ) continue;

		if( d[i] == 0 ) 
		{
			act[i] = false;
			++g0;
		}
		else
		{
			for( int j = i + 1; j <= n; ++ j )
			{
				if( act[j] && d[i] + d[j] == 0 )
				{
					act[i] = act[j] = false;
					++g0;
					break;
				}
			}
		}
		if( act[i] ) rd.pb( d[i] );
	}

	const int m = (int) rd.size();	

	vector< ll > sum( 1 << m );
	for( int mask = 1; mask < ( 1 << m ); ++ mask )
	{
		const int lt = mask & -mask;
		const int idx = __builtin_ctz( lt );
		sum[mask] = rd[idx] + sum[mask^lt];
	}

	vector< int > dp( 1 << m, -1 );
	function< int( int ) > go = [&]( int mask )
	{
		if( mask == 0 ) return 0;

		int &ref = dp[mask];
		if( ref != -1 ) return ref;
			
		ref = 0;

		int lt = mask & -mask;
		mask ^= lt;
		for( int sb = mask; sb; sb = ( sb - 1 ) & mask )
		{
			if( sum[sb | lt] == 0 )
				ref = max( ref, 1 + go( mask ^ sb ) );
		}

		return ref;
	};

	const int all = ( 1 << m ) - 1;
	g0 += go( all );
	cout << n + 1 - g0 << '\n';

	return 0;
}