public class Solution {

    public static void main(String []args)
    {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int step=0;
        int e=100;
        int k= scan.nextInt();
        int []a = new int[n+1];
        for(int i=0;i<n;i++)
        {
            a[i]= scan.nextInt();
        }
        
        while(true)
        {
            step +=k;
            step%=n;
              e--;
               if(a[step]==1)
                e-=2;
                if(step==0)
               break;
            
        }
        System.out.print(e);
    }
}

function jumpingOnClouds(c, k) {
    let i = 0;
    let energy = 100;
    do {
        if (c[i] == 1) energy -= 2;
        i = (i + k) % c.length;
        energy--;
    } while (i !== 0);

    return energy;
}