Or help the landlord in a non-mainstream way.
The breakthrough point is BB×BB=AAFF, and you are from 3 to 9, one after another, like 33*33= 1089, 44*44= 1936, because 22*22 is a three-digit number, and it is 8 after deduction.
That is, B=8, A=7 and F=4.
AA×BB=CAAC，77*88=6776，C=6
The rest is DD×EE=DFFD, which is equal to DD×EE=D44D.
D44D divided by DD, vertically divided on the draft. Take a look, d will be greater than 4. If it is less than or equal to 4, the number will be three digits, so it will be one of 5, 6, 7, 8 and 9.
As can be seen from the above, excluding 6, 7, 8 and d can only be 5 and 9.
Substitution, 5455 divided by 55=99.
Get D=5 and E=9.
A = 7
B = 8
C = 6
D = 5
E = 9
F = 4
Then A+B+C+D+E+F=4+5+6+7+8+9 = 39.