#include <bits/stdc++.h>
int main() {
  int a;
  scanf("%d", &a);
  int type1 = 0;
  int type2 = 0;
  int type3 = 0;
  int b = 1;
  int num;
  while (b != a + 1) {
    scanf("%d", &num);
    type1 += num;
    b++;
    if (b >= a + 1) {
      break;
    }
    scanf("%d", &num);
    type2 += num;
    b++;
    if (b >= a + 1) {
      break;
    }
    scanf("%d", &num);
    type3 += num;
    b++;
  }
  if (type2 >= type1) {
    if (type3 > type2) {
      printf("back");
      return 0;
    }
    if (type2 > type3) {
      printf("biceps");
      return 0;
    }
  }
  if (type2 < type1) {
    if (type3 >= type1) {
      printf("back");
      return 0;
    }
    if (type1 > type3) {
      printf("chest");
      return 0;
    }
  }
}
