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