#include <fstream>

using namespace std;
ifstream fin("sequencequery.in");
ofstream fout("sequencequery.out");
void citire ( int &,int &);
void ssm (int ,int );
int max ( int ,int );
int v[100000];
int main()
{
    int n,k,i,x,y;
    citire(n,k);
    for(i=0;i<k;i++)
    {
        fin>>x>>y;
        ssm (x,y);
    }
    return 0;
}

void ssm ( int a, int b)
{
    long long i,best[4],maxim;
    best[a%2]=v[a];
    maxim=v[a];
    for (i=a+1;i<=b;i++)
    {
        best[i%2]=max(v[i],best[!(i%2)]+v[i]);
        if(best[i%2]>maxim)
            maxim=best[i%2];
    }
        fout<<maxim<<"\n";
}


void citire (int &n,int &k)
{
    int i;
    fin>>n>>k;
    for(i=1;i<=n;i++)
        fin>>v[i];
}
int max ( int a,int b)
{
    if (a>b)
        return a;
    return b;
}