#include <stdio.h>
#include <stdlib.h>
#include <string.h>



int sum_stride(int *arr, int n, int k) {
    // TODO: implement this function using pointer arithmetic
    (void) arr;
    (void) n;
    (void) k;
    return 0;
}


int main(void) {
    int n;
    if (scanf("%d", &n) != 1) { n = 0; }
    int arr[1000];
    for (int i = 0; i < n; i++) { scanf("%d", &arr[i]); }
    int k;
    if (scanf("%d", &k) != 1) { k = 1; }
    printf("%d\n", sum_stride(arr, n, k));
    return 0;
}