题解 | 【模板】前缀和

#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
const int N = 1e5 + 10;

//int a[N];
ll pre[N];

int main(){
	int n,m;  cin >> n >> m;
	
	for(int i = 1 ; i <= n ; i++){
		int a;  cin >> a;
		pre[i] = pre[i-1]+a;
	}
	
	while(m--){
		int l,r;  cin >> l >> r;
		cout << pre[r] - pre[l-1] << endl;
	}
	
	return 0;
}