Расстояние Левенштейна

a = input()
b = input()
a, b = list(a), list(b)
n = len(a)
m = len(b)
F = [[0] * (m + 1) for i in range(n + 1)]
for i in range(1,n+1):
    for j in range(1,m+1):
        if a[i-1] == b[j-1]:
            F[i][j] = F[i-1][j-1]
        else:
            F[i][j] = min(F[i-1][j] + 1, F[i][j-1] + 1, F[i-1][j-1] + 1)
print(F[n][m])