"""Let G=(V,E) be a directed Graph.
Check whether the given Graph is a tree or not."""
import time
t0=time.clock()
import sys
a=[]
b=[]
c=[]
d=[]
fi=open("in19_8.txt",'r')
w=open("out_18_19_8.txt",'w')
count=0
for row in fi:
    list=row.split(" ")
    if count==0:
        for i in list:
            a.append(int(i))
    if count==1:
        for i in list:
            b.append(int(i))
    if count==2:
        for i in list:
            c.append(int(i))
    if count==3:
        for i in list:
            d.append(int(i))
    count+=1
print a,b,c,d 
flag=0
if a[0]==0:
    flag=0
else:
    flag=flag+1
if b[1]==0:
    flag=0
else:
    flag=flag+1
if c[2]==0:
    flag=0
else:
    flag=flag+1
if d[3]==0:
    flag=0
else:
    flag=flag+1
if flag!=0:
    print "not a tree"
    w.write("not a tree")
    
else:
    f=0
    if a[1]==1 :
        if b[0]>=1:
            f=f+1
        else:
            if a[2]==1:
                if c[0]>=1:
                    f=f+1
                else:
                    if a[3]==1:
                        if d[0]>=1:
                            f=f+1
                        else:
                            if f>=1:
                                print"not a tree"
                                w.write("not a tree")
                            else:
                                 f=0
                                 if b[0]==1:
                                    if a[1]>=1:
                                        f=f+1
                                    else:
                                        if b[2]==1:
                                           if c[1]>=1:
                                                    f=f+1
                                           else:
                                                if b[3]==1:
                                                    if d[1]>=1:
                                                        f=f+1
                            
if f>=1:
    print"not a tree"
    w.write("not a tree")
else:
    f=0
    if c[0]==1:
        if a[2]>=1:
            f=f+1
        else:
            if c[1]==1:
                if b[2]>=1:
                    f=f+1
                else:
                    if c[3]==1:
                        if d[2]>=1:
                            f=f+1
                    else:
                        if f>=1:
                            print"not a tree"
                            w.write("not a tree")
                        else:
                             f=0
                             if d[0]==1:
                                if a[3]>=1:
                                    f=f+1
                                else:
                                    if d[1]==1:
                                        if b[3]>=1:
                                            f=f+1
                                        else:
                                             if d[2]==1:
                                                if c[3]>=1:
                                                        f=f+1
                                                else:
                                                    if f>=1:
                                                        print"not a tree"
                                                        w.write("not a tree")
                                                    else:
                                                        print"it is a tree"
                                                        w.write("it is a tree")

t1=time.clock()
t2=t1-t0
print t2
w.write('\n'+"time used="+repr(t2))
mem=sys.getsizeof(t0)+sys.getsizeof(t1)+sys.getsizeof(t2)+sys.getsizeof(i)+36
print mem
w.write('n'+"memory used="+repr(mem))
fi.close()
w.close()