n = int(input())
s = input().strip()

if n == 0:
    print(0)
    exit()

# Split the string into runs
runs = []
current = s[0]
for c in s[1:]:
    if c != current:
        runs.append(current)
        current = c
runs.append(current)

# Count the frequency of each run's color
from collections import defaultdict
freq = defaultdict(int)
for c in runs:
    freq[c] += 1

max_freq = max(freq.values())
answer = (len(runs) - max_freq) + 1

print(answer)