#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a[51], i, j, c = 0, b = 0, d = 0;
  memset(a, 0, sizeof(a));
  scanf("%d", &n);
  for (i = 1; i <= n; i++) {
    scanf("%d", &a[i]);
    if (i % 3 == 1)
      c += a[i];
    else if (i % 3 == 2)
      b += a[i];
    else
      d += a[i];
  }
  if (c > b && c > d)
    printf("chest\n");
  else if (b > c && b > d)
    printf("biceps\n");
  else
    printf("back\n");
  return 0;
}
