rt，只求个暴力分，WA 不明白，样例咋还有负数嘞？

#include <iostream>
using namespace std;
using LL = long long;
const int N = 1e5 + 10;
LL a[N], s[N], ans[N];
int main()
{
    int n, q;
    cin >> n >> q;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        s[i] = s[i - 1] + a[i];
    }
    for (int i = 1; i <= n; i++)
        ans[i] = ans[i - 1] ^ s[i];
    while (q--) {
        int l, r;
        cin >> l >> r;
        cout << ans[r] - ans[l - 1] << endl;
    }
    return 0;
}