import sys
sys.setrecursionlimit(200050)
from functools import lru_cache

@lru_cache(maxsize=1000000)
def f(x, y):
    if x == 0:
        return y
    if y == 0:
        return x
    if S[x - 1] == T[y - 1]:
        return f(x - 1, y - 1)
    else:
        return min(f(x - 1, y), f(x, y - 1), f(x - 1, y - 1)) + 1

n, m = map(int, input().split())
S = input()
T = input()
print(f(n, m))