前缀和

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

const int N=1e5+10;
int a[N];
int d[N];

inline int read() {
  int x = 0;
  int f = 1;
  char ch = getchar();
  while (!isdigit(ch)) {
    if (ch == '-') f = -1;
    ch= getchar();
  }
  while (isdigit(ch)) {
    x = x*10 + ch-'0';
    ch = getchar();
  }
  return x * f;
}

int main() {
  int n = read(), m = read();
  for (int i=1; i<=n; ++i) a[i] = read();
  d[1] = a[1];
  for (int i=2; i<=n; ++i) 
    d[i] = d[i-1] + a[i];
  while (m --) {
    int a=read(), b=read();
    printf("%d\n", d[b]-d[a-1]);
  }
  return 0;
}