a = input()
b = input()
la = len(a)
lb = len(b)
#建立二维列表，行数la+1，列数lb+1,初值为0
res = [[0] * (lb + 1)] * (la + 1)
mmax = 0
for i in range(1, la+1):
for j in range(1, lb+1):
if a[i-1] == b[j-1]:
res[i][j] = res[i-1][j-1] + 1
if(res[i][j]>mmax):
mmax = res[i][j]
print(mmax)
https://blog.csdn.net/alun550/article/details/106960144
参考一下这个