#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

#define DIM 5005

int V[DIM], x[DIM], df[DIM];

//andrei1998 (C)
class InputReader {
public:
    InputReader(const char *input_file) {
        in = fopen(input_file, "r");
        cursor = 0;
        fread(buffer, 1, SZ, in);
    }

    InputReader& operator>>(int &nr) {
        while (!isdigit(buffer[cursor]))
            advance();

        nr = 0;
        while (isdigit(buffer[cursor])) {
            nr *= 10;
            nr += buffer[cursor] - '0';
            advance();
        }

        return (*this);
    }

private:
    static const int SZ = (1 << 20);
    FILE *in;
    int cursor;
    char buffer[SZ + 5];

    void advance() {
        ++ cursor;
        if (cursor == SZ) {
            cursor = 0;
            fread(buffer, 1, SZ, in);
        }
    }
};


int main() {
    InputReader cin("secv.in");
    freopen("secv.out","w",stdout);

    int N;
    cin >> N;

    for(int i = 1; i <= N; ++i) {
        cin >> V[i];
        x[i] = V[i];
    }
    sort(x + 1, x + 1 + N);
    x[0] = -1;
    for(int i = 1; i <= N; ++i) {
        if(x[i] > x[i - 1]) {
            df[++df[0]] = x[i];
        }
    }

    int ans = 1e9;
    for(int i = 1; i <= N; ++i) {
        if(df[1] == V[i]) {
            int pos = 2, j = i + 1;
            for(; pos <= df[0] && j <= N; ++j) {
                if(V[j] == df[pos]) {
                    ++pos;
                }
            }

            if(pos > df[0]) {
                ans = min(ans, j - i);
            }
        }
    }

    if(ans == 1e9) {
        cout << -1 << '\n';
        return 0;
    }

    cout << ans << '\n';

    return 0;
}