import sys
input = sys.stdin.readline

N, M, S = int(input()), int(input()), input().rstrip()
result = OIcount = i = 0

while i < M-1:
    if S[i:i+3] == "IOI":
        OIcount += 1
        i += 2
        
        if OIcount == N:
            result += 1
            OIcount -= 1
    else:
        OIcount = 0
        i += 1

print(result)