1240  Yet Another A+B Problem
Time Limit : 10 Second
Memory Limit : 128 MB
Submission: 139
Solved: 34
 Description
 We all have come across A+B Problem many times. This time, you are to solve another A+B Problem. An addition rebus is a puzzle where you get an addition equation, like "ABC+CBA=BDB". And you need to replace each letter with a digit (from 0 through 9) in such a way that:
 Equal letters are replaced with equal digits.
 Different letters are replaced with different digits.
 None of the resulting numbers starts with 0, unless the entire number is just 0.
 The resulting equation holds.
Now you are given N addition rebuses, and you are to tell me the maximum number X that there exists a map from each letter to a digit satisfying first X equations but there exists none satisfying first X+1 equations. If there exists a sequence satisfying all the given equations, then number X should be the number of all the equations given. And if there exists none sequence satisfying the first equation, then number X should be 0.  Input
 The input consists of multiple test cases. The first line of input contains an integer T (T <= 10), which is the number of test cases.
The first line of each test case contains the number N (N <= 10), indicating the total number of equations.
The next N line each contains an addition rebus described above. Equations are consisted of numbers (represented by capital letters) and operators ("+" and "="). You can assume that there exists no more than 10 different letters in each test case and the length of each number is a positive integer less or equal to 20.  Output
 For each test case, your program should output one line containing the maximum number X as we described above.
 sample input

2 2 AAA+BBB=CCC AAA+CCC=DDD 3 ABC+CBA=DDD AAA+BBB=EEE ABA+CBC=EEE
 sample output

2 2
 hint
 source
 <a href="http://aifreedom.com/">Ai.Freedom</a>