难道不是这么写吗

#include <bits/stdc++.h>
using namespace std;
long long pre[100005], n, m, a[100005], l, r;
int main() {	
	cin >> n;
	for(long long i = 1; i <= n; i ++) {
		cin >> a[i];
		pre[i] = pre[i - 1] + a[i];
	}
	cin >> m;
	for(long long i = 1; i <= m; i ++) {
		cin >> l >> r;
		cout << pre[r] - pre[i - 1] << "\n";
	}
	return 0;
}