#int(input()) #map(int, input().split()) #list(map(int, input().split())) N = int(input()) S = input() m = 3 * N a = ("c", "o", "n") c = [[0] * 3 for i in range(3)] for i in range(m): if S[i] in a: t = a.index(S[i]) c[i%3][t] += 1 # for i in range(3): # print(c[i]) ans = 0 u = [] for i in range(3): b = 1000000 for j in range(3): b = min(c[(i+j)%3][j], b) # print((i+j)%3, j) u.append(b) if sum(u) == N: if u[0] == N: print(u[0]) else: print(N-1) else: print(sum(u))