Input 
4 5
abcde
abcde
abcde
abcde
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1
Output 
3
Input 
4 3
abc
aba
adc
ada
10 10 10
10 1 10
10 10 10
10 1 10
Output 
2
Input 
3 3
abc
ada
ssa
1 1 1
1 1 1
1 1 1
Output 
0