#include <bits/stdc++.h>
int main() {
  int n, i, j, k, c = 0, bc = 0, bk = 0;
  scanf("%d", &n);
  int ar[n];
  for (i = 0; i < n; i++) {
    scanf("%d", &ar[i]);
  }
  for (i = 0, j = 1, k = 2; i < n || j < n || k < n; i += 3, j += 3, k += 3) {
    if (i < n) c += ar[i];
    if (j < n) bc += ar[j];
    if (k < n) bk += ar[k];
  }
  if (c >= bc && c >= bk) printf("chest\n");
  if (bc >= c && bc >= bk) printf("biceps\n");
  if (bk >= c && bk >= bc) printf("back\n");
  return 0;
}
