#https://gist.github.com/vineetrok/1391954  
  
import math  
  
def distance(a,b):  
    x=float(a[0])-float(b[0])  
    x=x*x  
    y=float(a[1])-float(b[1])  
    y=y*y  
    dist=round(math.sqrt(x+y),2)  
    return dist  
  
def minimum(matrix):  
    p=[0,0]  
    mn=1000  
    for i in range(0,len(matrix)):          
        for j in range(0,len(matrix[i])):              
            if (matrix[i][j]>0 and matrix[i][j]<mn):  
                mn=matrix[i][j]  
                p[0]=i  
                p[1]=j  
    return p   
              
def newpoint(pt):  
    x=float(pt[0][0])+float(pt[1][0])  
    x=x/2  
    y=float(pt[0][1])+float(pt[1][1])  
    y=y/2  
    midpoint=[x,y]  
    return midpoint  
  
if __name__ == '__main__':      
    n=int(input("Input number of points.> "))  
    points=list()  
    outline='['  
    i=0  
  
    while(i<n):  
        s=input("Input point (eg. 1,1)"+chr(65+i)+"> ")  
        c=s.split(",")  
        points.append(c)  
        i=i+1  
  
    names={}  
  
    for i in range(0,len(points)):  
        names[str(points[i])]=chr(65+i)  
    l=0  
    while(len(points)>1):  
        l=l+1  
        matrix=list()  
        print('Distance matrix no. '+str(l)+': ')  
        for i in range(0,len(points)):  
            m=[]  
            for j in range(0,len(points)):  
                m.append(0)  
            for j in range(0,len(points)):  
                m[j]=distance(points[i],points[j])  
            print(str(m))  
            matrix.append(m)  
          
        m=minimum(matrix)  
        pts=list()  
        p1=points[m[0]]  
        pts.append(p1)  
        points.remove(p1)  
        p2=points[m[1]-1]  
        pts.append(p2)  
        points.remove(p2)     
        midpoint=newpoint(pts)  
        points.append(midpoint)      
        c1=names.pop(str(p1))  
        c2=names.pop(str(p2))  
        names[str(midpoint)]="["+str(c1)+str(c2)+"]"      
        outline=names[str(midpoint)]  
          
    print("Cluster is :",names[str(midpoint)])