从简单题开始慢慢来

#include <iostream>

using namespace std;

const int N = 100010;

int n,m;
int a[N],s[N];

int main(){
    cin>>n>>m;
    for (int i = 1; i <= n;i ++){
        cin>>a[i];
        s[i] = s[i-1]+a[i];
    } 

    while (m--){
        int l,r,res;

        cin>>l>>r;
        res = s[r]-s[l-1];
        cout<<res<<endl;
    }

    return 0;
}