#include <fstream>

using namespace std;
ifstream cin ("transport.in");
ofstream cout ("transport.out");

int v[16001];

int main()
{
    int n,k,mij=0,st,dr,i,maxi=0,suma;
    cin>>n;
    cin>>k;
    for(i=1; i<=n; i++)
    {
        cin>>v[i];
        if(v[i]>maxi)
            maxi=v[i];
        suma=v[i]+suma;
    }
    st=maxi;
    dr=suma;
    int sol=-1;

    while(st<=dr)
    {

        mij=(st+dr)/2;
        p=0;
        if()

    }
    cout<<sol;

    return 0;
}