#include<fstream>
#include<algorithm>
using namespace std;
int n,i,j,lg,minim,poz,m,ok;
unsigned long v[5005],u[5005];
int main()
{
	ifstream f("secv.in");
	ofstream g("secv.out");
	f>>n;
	for(i=1;i<=n;++i)
	{
		f>>v[i];
		u[i]=v[i];
	}
	sort(u+1,u+n+1);
	minim=5005;
	for(i=1;i<=n;++i)
		if(u[i]!=u[i-1])
		{
			++m;
			u[m]=u[i];
		}
		lg=50005;
		for(i=1;i<=n&&!ok;++i)
		{
			poz=1;
			for(j=i;j<=n;++j)
				if(u[poz]==v[j])
				{
					++poz;
				    if(poz==m+1)
						break;
				}
				
				if(poz==m+1&&j-i+1<=n)
					lg=j-i+1;
		}
		
		if(lg==5005)
			g<<-1;
		else
			g<<lg<<"\n";
			
		
		return 0;
}