#include <bits/stdc++.h>

using namespace std;

const int NMAX = 100010;

int N, Q;
int V[NMAX], ST[4 * NMAX];
int lastSeen[NMAX];
int answer[NMAX];
vector<pair<int, int>> queryList[NMAX];

void updateTree(int node, int left, int right, int pos, int value) {
	if (left == right) {
		ST[node] = value;
		return;
	}
	int mid = (left + right) / 2;
	if (pos <= mid)
		updateTree(node * 2, left, mid, pos, value);
	else
		updateTree(node * 2 + 1, mid + 1, right, pos, value);
	ST[node] = max(ST[node * 2], ST[node * 2 + 1]);
}

int queryTree(int node, int left, int right, int qleft, int qright) {
	if (left >= qleft && right <= qright)
		return ST[node];
	int mid = (left + right) / 2;
	int answer = -1;
	if (qleft <= mid)
		answer = max(answer, queryTree(node * 2, left, mid, qleft, qright));
	if (qright > mid)
		answer = max(answer, queryTree(node * 2 + 1, mid + 1, right, qleft, qright));
	return answer;
}

int main() {
	assert(freopen("pq.in", "r", stdin));
	assert(freopen("pq.out", "w", stdout));
	int i;
	memset(ST, -1, sizeof ST);
	memset(lastSeen, -1, sizeof lastSeen);
	scanf("%d %d", &N, &Q);
	for (i = 1; i <= N; ++i)
		scanf("%d", &V[i]);
	for (i = 1; i <= Q; ++i) {
		int x, y;
		scanf("%d %d", &x, &y);
		queryList[y].push_back({x, i});
	}
	for (i = 1; i <= N; ++i) {
		if (lastSeen[V[i]] != -1)
			updateTree(1, 1, N, lastSeen[V[i]], i - lastSeen[V[i]]);
		lastSeen[V[i]] = i;
		for (const auto &it: queryList[i])
			answer[it.second] = queryTree(1, 1, N, it.first, i);
	}
	for (i = 1; i <= Q; ++i)
		cout << answer[i] << '\n';
	return 0;
}