#include <bits/stdc++.h>
int main() {
  int n, t, a[3] = {0, 0, 0};
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    scanf("%d", &t);
    a[i % 3] += t;
  }
  if (a[0] > a[1]) {
    if (a[0] > a[2])
      printf("chest");
    else
      printf("back");
  } else if (a[1] > a[2])
    printf("biceps");
  else
    printf("back");
}
