import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.ArrayList;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author puneet
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastInput in = new FastInput(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    }

    static class Task {
        public void solve(int testNumber, FastInput in, PrintWriter out) {
            int t = in.ni();
            while (t-- > 0) {
                int n = in.ni();
                ArrayList<Integer>[] list = new ArrayList[n + 1];
                for (int i = 0; i < n + 1; ++i) {
                    list[i] = new ArrayList<>();
                }

                for (int i = 1; i <= n; ++i) {
                    int a = in.ni();
//                out.println(a);
                    list[a].add(i);
                }
                boolean isok = false;
                for (int i = 1; i <= n; ++i) {
                    if (list[i].size() != 1) {
                        isok = true;
                    }
                }

                if (!isok) {
                    out.println("-1");
                    continue;
                }
                int max = Integer.MAX_VALUE;
                for (int i = 1; i <= n; ++i) {
                    for (int j = 0; j < list[i].size() - 1; ++j) {
                        max = Math.min(max, list[i].get(j + 1) - list[i].get(j) + 1);
                    }
                }

                out.println(max);
            }
        }

    }

    static class FastInput {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private FastInput.SpaceCharFilter filter;

        public FastInput(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int ni() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }
}

