#include <fstream>
#include <algorithm>
#include <vector>

using namespace std;

const int MAX_N = 5 * 1e3;
int a[MAX_N + 1];
vector<int> v;
int n;

int main() {
    ifstream fin("secv.in");
    ofstream fout("secv.out");
    fin >> n;
    for (int i = 1; i <= n; i++) {
        fin >> a[i];
    }
    sort(a + 1, a + n + 1);
    a[0] = -1;
    for (int i = 1; i <= n; i++) {
        if (a[i] != a[i - 1]) {
            v.push_back(a[i]);
        }
    }
    int answer = (1 << 30);
    for (int i = 1; i <= n; i++) {
        if (a[i] != v[0]) {
            continue;
        }
        int k = 1;
        for (int j = i + 1; j <= n; j++) {
            if (a[j] == v[k]) {
                k++;
            }
            if (k == v.size()) {
                answer = min(answer, j - i + 1);
                break;
            }
        }
    }
    if (answer == (1 << 30)) {
        fout << "-1";
    }
    fout << answer;
    return 0;
}