Mitsuami

#include<bits/stdc++.h>

using namespace std;

#define ll long long

/*

hi, I'm rintaro.

AC is right

AC count is my life

But don't solve too many easy plobems!

*/

int main() {

  //writerの確認コード

  ll N, Q;

  cin >> N >> Q;

  vector<ll> A(N+1,0);

  for(int i = 1; i <= N; i++) cin >> A[i];

  //累積和配列にする

  for(int i = 1; i <= N; i++) A[i] += A[i - 1];

  //クエリ処理

  ll sum = 0;

  for(int i = 0; i < Q; i++) {

    ll L, R;

    cin >> L >> R;

    sum += (A[R] - A[L - 1]) * (R - L);

  }

  cout << sum << endl;

}