PROGRAMMING:Number of circles of friends
There are n students in the school. Many students have become friends in their study and life. It is said that the relationship between friends has reflexivity (you and yourself are friends), symmetry (you and I are friends, you and I must be friends), and transitivity. That is to say, if a and B are friends, and B and C are friends, then a and C are friends, so many circles of friends are formed. The following matrix shows four people's circle of friends: row I, column J, 1 means direct friendship, 0 means not direct friendship, whether it is indirect friend is not clear. In the input example, 0, 1, 2 are a circle of friends, and No. 3 is a circle of friends. So there are two circles of friends. Please write a program, according to the given relationship matrix, calculate the number of school circle of friends.
Note: because the relationship matrix is symmetric, only the data of the lower triangle is entered, that is, only the friend relationship between student I and the students in front of him is described, and the relationship behind him is not repeated (including himself on the diagonal: n students, only n * (n + 1) / 2 data are entered).
###Input example:
```in
four
one
1 1
1 0 1
0 0 0 1
```
###Output example:
Output the number of circle of friends in the whole school (refers to the circle of friends without intersection): 1
```out
two
```
answer：If there is no answer, please comment
Note: because the relationship matrix is symmetric, only the data of the lower triangle is entered, that is, only the friend relationship between student I and the students in front of him is described, and the relationship behind him is not repeated (including himself on the diagonal: n students, only n * (n + 1) / 2 data are entered).
###Input example:
```in
four
one
1 1
1 0 1
0 0 0 1
```
###Output example:
Output the number of circle of friends in the whole school (refers to the circle of friends without intersection): 1
```out
two
```
answer：If there is no answer, please comment