import java.io.*;
import java.util.*;

public class C implements Runnable {
	public static void main (String[] args) {new Thread(null, new C(), "_cf", 1 << 28).start();}

	public void run() {
		FastScanner fs = new FastScanner();
		PrintWriter out = new PrintWriter(System.out);
		System.err.println("");

		int T = fs.nextInt();
		int MAX = 200200;
		int[] nxt = new int[MAX];
		int[] last = new int[MAX];
		Arrays.fill(last, -1);
		
		while(T-->0) {
			int n = fs.nextInt();
			int[] a = fs.nextIntArray(n);
			if(n == 1) {
				out.println(-1);
				continue;
			}
			
			boolean two = false;
			for(int i = 0; i < n-1; i++) {
				if(a[i] == a[i+1]) {
					two = true;
				}
			}
			if(two) {
				out.println(2);
				continue;
			}

			int[] where = new int[n];
			for(int i = n-1; i >= 0; i--) {
				if(last[a[i]] == T) {
					where[i] = nxt[a[i]];
				}
				else {
					where[i] = -1;
				}
				last[a[i]] = T;
				nxt[a[i]] = i;
			}
			
			int res = n+n;
			for(int i = 0; i < n; i++) {
				if(where[i] != -1) {
					res = Math.min(res, where[i]-i+1);
				}
			}
			if(res >= n+n) res = -1;
			out.println(res);
			
		}
		
		out.close();
	}

	class FastScanner {
		public int BS = 1<<16;
		public char NC = (char)0;
		byte[] buf = new byte[BS];
		int bId = 0, size = 0;
		char c = NC;
		double num = 1;
		BufferedInputStream in;

		public FastScanner() {
			in = new BufferedInputStream(System.in, BS);
		}

		public FastScanner(String s) {
			try {
				in = new BufferedInputStream(new FileInputStream(new File(s)), BS);
			}
			catch (Exception e) {
				in = new BufferedInputStream(System.in, BS);
			}
		}

		public char nextChar(){
			while(bId==size) {
				try {
					size = in.read(buf);
				}catch(Exception e) {
					return NC;
				}                
				if(size==-1)return NC;
				bId=0;
			}
			return (char)buf[bId++];
		}

		public int nextInt() {
			return (int)nextLong();
		}

		public long nextLong() {
			num=1;
			boolean neg = false;
			if(c==NC)c=nextChar();
			for(;(c<'0' || c>'9'); c = nextChar()) {
				if(c=='-')neg=true;
			}
			long res = 0;
			for(; c>='0' && c <='9'; c=nextChar()) {
				res = (res<<3)+(res<<1)+c-'0';
				num*=10;
			}
			return neg?-res:res;
		}

		public double nextDouble() {
			double cur = nextLong();
			return c!='.' ? cur:cur+nextLong()/num;
		}

		public String next() {
			StringBuilder res = new StringBuilder();
			while(c<=32)c=nextChar();
			while(c>32) {
				res.append(c);
				c=nextChar();
			}
			return res.toString();
		}

		public String nextLine() {
			StringBuilder res = new StringBuilder();
			while(c<=32)c=nextChar();
			while(c!='\n') {
				res.append(c);
				c=nextChar();
			}
			return res.toString();
		}

		public boolean hasNext() {
			if(c>32)return true;
			while(true) {
				c=nextChar();
				if(c==NC)return false;
				else if(c>32)return true;
			}
		}
		
		public int[] nextIntArray(int n) {
			int[] res = new int[n];
			for(int i = 0; i < n; i++) res[i] = nextInt();
			return res;
		}
		
	}

}