#include <bits/stdc++.h>
int main() {
  int p[3] = {0};
  int n, a, k = 0;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    scanf("%d", &a);
    p[k++] += a;
    if (k == 3) k = 0;
  }
  int max = 0;
  for (int i = 0; i < 3; i++) {
    if (p[i] > max) {
      max = p[i];
      k = i;
    }
  }
  if (k == 0)
    printf("chest");
  else if (k == 1)
    printf("biceps");
  else
    printf("back");
  return 0;
}
