题目

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define fi first
#define se second
#define lson p << 1
#define rson p << 1 | 1
#define ll long long
#define pii pair<int, int>
#define ld long double
const int maxn = 1e6 + 5, inf = 1e18, maxm = 4e4 + 5, base = 37;
const int N = 1e5 + 5;
const int mod = 1e9 + 7;
// const int mod = 998244353;
// const __int128 mod = 212370440130137957LL;
int n, m;

int t[maxn];//树状数组维护区间 所有 不同数字 的异或和
int lowbit(int x){
	return x & -x;
}

void add(int x, int k){
	for(int i = x; i <= n; i += lowbit(i)){
		t[i] ^= k;
	}
}
int ask(int x){
	int res = 0;
	for(int i = x; i >= 1; i -= lowbit(i)){
		res ^= t[i];
	}
	return res;
}

//long long ? maxn ? n? m?
void solve(){
    ll res = 0;
    int k, q;
    cin >> n >> q;
	vector<int> a(n + 1), lst(n + 1), ans(q + 1), pre(n + 1);
	for(int i = 1; i <= n; i++){
		cin >> a[i];
		pre[i] = pre[i - 1] ^ a[i];
	}
	vector<vector<pii>> qry(n + 1);
	for(int i = 1; i <= q; i++){
		int l, r;
		cin >> l >> r;
		qry[r].pb({l, i});
	}
	map<int, int> mp;//数字最后出现的位置
	for(int i = 1; i <= n; i++){
		if(mp.count(a[i])){
			add(mp[a[i]], a[i]);
		}
		add(i, a[i]);
		mp[a[i]] = i;
		for(auto [l, id] : qry[i]){
			int r = i;
			ans[id] = ask(r) ^ ask(l - 1) ^ pre[r] ^ pre[l - 1];
		}
	}
	for(int i = 1; i <= q; i++){
		cout << ans[i] << '\n';
	}
}
    
signed main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout << fixed << setprecision(9);
    
    int T = 1;
    // cin >> T;
    while (T--){
        solve();
    }
    return 0;
}