# 計算量 O(いっぱい)

from collections import defaultdict, deque

n = int(input())
s = input()
cost = defaultdict(int)
cost[s] = 0
goal = "".join(sorted(list(s)))
que = deque([s])
while que:
  t = que.popleft()
  if t == goal:
    exit(print(cost[t]))
  t1 = t[-1] + t[:-1]
  t2 = t[0] + t[-1] + t[1:-1]
  if t1 not in cost:
    cost[t1] = cost[t] + 1
    que.append(t1)
  if t2 not in cost:
    cost[t2] = cost[t] + 1
    que.append(t2)