795. 前缀和
#include<iostream>
using namespace std;
const int N = 1e5 + 10;
int n, m;
int a[N];
int main()
{
scanf("%d%d", &n, &m);
for(int i = 1; i <= n; i++) scanf("%d", &a[i]), a[i] = a[i] + a[i - 1];
while(m--)
{
int l, r; scanf("%d%d", &l, &r);
printf("%d\n", a[r] - a[l - 1]);
}
return 0;
}