#include <fstream>
#include <iostream>
#include <algorithm>

#define pb push_back
#define f first
#define s second
#define pii pair<int, int>
#define mp make_pair
 
using namespace std;
 
const string name = "secv",
             in_file = name + ".in",
             out_file = name + ".out";
 
ifstream fin(in_file);
ofstream fout(out_file);
 
const int MAX = 5e3 + 5;

pii old[MAX];
int v[MAX], poz[MAX][MAX], current[MAX], length[MAX];
int n;

int main() {
	fin >> n;
	for (int i = 1; i <= n; i++) {
		fin >> old[i].f;
		old[i].s = i;
	}

	sort(old + 1, old + n + 1);

	int cnt = 1;
	v[old[1].s] = cnt;
	for (int i = 2; i <= n; i++) {
		if (old[i].f != old[i - 1].f) 
			cnt++;
		v[old[i].s] = cnt;
	}

	for (int i = 1; i <= cnt; i++)
		current[i] = 1;

	for (int i = 1; i <= n; i++) 
		poz[v[i]][++length[v[i]]] = i;
	
	int sol = (1 << 30) - 1;
	for (; current[1] <= length[1]; current[1]++) {
		int j = 2;
		for (; j <= cnt; j++) {
			while (current[j] <= length[j] && poz[j][current[j]] < poz[j - 1][current[j - 1]]) {
				//cout << "poz[" << j << "][" << current[j] << "] < poz[" << j - 1 << "][" << current[j - 1] << "]\n";
				current[j]++;
			}

			if (current[j] > length[j]) {
				fout << (sol == (1 << 30) - 1 ? -1: sol);
				return 0;
			}
		}
		sol = min(sol, poz[cnt][current[cnt]] - poz[1][current[1]] + 1);
		//cout << poz[cnt][current[cnt]] << ' ' << poz[1][current[1]] << endl;
	}
	fout << (sol == (1 << 30) - 1 ? -1 : sol);
	return 0;
}