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