var firstInput = Console.ReadLine()

    .Split(' ')

    .Select((i) => int.Parse(i))

    .ToArray();

​

var cpuCount = firstInput[0];

var taskCount = firstInput[1];

var cpusEnergy = Console.ReadLine()

    .Split(' ')

    .Select((i) => new Cpu(int.Parse(i)))

    .ToList();

​

var sortedCpus = cpusEnergy

    .OrderBy((c) => c.Cost)

    .ToList();

​

for (int i = 0; i < taskCount; i++)

{

    var taskInfo = Console.ReadLine()

        .Split(' ')

        .Select((t) => int.Parse(t))

        .ToArray();

​

    var time = taskInfo[0];

    var taskRemainingTime = taskInfo[1];

    foreach (var cpu in sortedCpus)

    {

        cpu.SetCurrentTime(time);

        if (cpu.IsFree())

        {

            cpu.SetTask(taskRemainingTime);

            break;

        }

    }

}

​

foreach (var cpu in sortedCpus)

{

    cpu.SetCurrentTime(1000000001);

}

​

Console.WriteLine(Cpu.CommonEnergyLoss);

​

class Cpu

{

    public int Cost;

    public int TaskRemainingTime;

    public int LastTime;

    // public int TotalProductiveTime;

    public static long CommonEnergyLoss;

    public Cpu(int cost)

    {

        Cost = cost;

    }

​

    public void SetCurrentTime(int time)

    {

        var workTime = time - LastTime;

        if (workTime < TaskRemainingTime)

        {

            // TotalProductiveTime += workTime;

            CommonEnergyLoss += workTime * Cost;

            TaskRemainingTime -= workTime;

            LastTime = time;

            return;

        }

​

        if (workTime >= TaskRemainingTime)

        {

            // TotalProductiveTime += TaskRemainingTime;

            CommonEnergyLoss += TaskRemainingTime * Cost;

            TaskRemainingTime = 0;

            LastTime = time;

            return;

        }

    }

​

    public void SetTask(int time)

    {

        TaskRemainingTime = time;

    }

​

    public bool IsFree()

    {

        return TaskRemainingTime == 0;

    }

}