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