Buggy python submission (verdict: Time Limit Exceeded):
n,m=map(int,input().split())
templ=[0]*m
temp=[]
tempb=[]
ans=0
for i in range(0,m):
  a,b=map(int,input().split())
  templ[i]=[a,b]
  if a==1:
    if b==n:
      print("POSSIBLE")
      ans=1
      break
    else:
      temp.append(b)
  if b==n:
    tempb.append(a)
if len(temp)>=1 and ans==0:
  c = [x for x in temp if x in tempb]
  if len(c)>=1:
    print("POSSIBLE")
  else:
    print("IMPOSSIBLE")
  """
  for i in range(0,len(tempb)):
    if tempb[i] in temp:
      print("POSSIBLE")
      break
  """
else:
  print("IMPOSSIBLE")            
    

Fixed submission:
n,m=map(int,input().split())
templ=[0]*m
temp=[]
tempb=[]
ans=0
for i in range(0,m):
  a,b=map(int,input().split())
  templ[i]=[a,b]
  if a==1:
    if b==n:
      print("POSSIBLE")
      ans=1
      break
    else:
      temp.append(b)
  if b==n:
    tempb.append(a)
if len(temp)>=1 and ans==0:
  temp=set(temp)
  tempb=set(tempb)
  c = temp&tempb
  #c = [x for x in temp if x in tempb]
  if len(c)>=1:
    print("POSSIBLE")
  else:
    print("IMPOSSIBLE")
  """
  for i in range(0,len(tempb)):
    if tempb[i] in temp:
      print("POSSIBLE")
      break
  """
else:
  print("IMPOSSIBLE")

Buggy python submission (verdict: Time Limit Exceeded):
n,m=map(int,input().split())
templ=[0]*m
temp=[]
tempb=[]
ans=0
for i in range(0,m):
  a,b=map(int,input().split())
  templ[i]=[a,b]
  if a==1:
    if b==n:
      print("POSSIBLE")
      ans=1
      break
    else:
      temp.append([b,n])
  if b==n:
    tempb.append([a,b])
if len(temp)>=1 and ans==0:
  """
  c = [x for x in tempb if x in templ]
  if len(c)>=1:
    print("POSSIBLE")
  """
  for i in range(0,len(tempb)):
    if tempb[i] in temp:
      print("POSSIBLE")
      break
  else:
    print("IMPOSSIBLE")
else:
  print("IMPOSSIBLE")            
    

Fixed submission:
n,m=map(int,input().split())
templ=[0]*m
temp=[]
tempb=[]
ans=0
for i in range(0,m):
  a,b=map(int,input().split())
  templ[i]=[a,b]
  if a==1:
    if b==n:
      print("POSSIBLE")
      ans=1
      break
    else:
      temp.append(b)
  if b==n:
    tempb.append(a)
if len(temp)>=1 and ans==0:
  temp=set(temp)
  tempb=set(tempb)
  c = temp&tempb
  #c = [x for x in temp if x in tempb]
  if len(c)>=1:
    print("POSSIBLE")
  else:
    print("IMPOSSIBLE")
  """
  for i in range(0,len(tempb)):
    if tempb[i] in temp:
      print("POSSIBLE")
      break
  """
else:
  print("IMPOSSIBLE")

Buggy python submission (verdict: Time Limit Exceeded):
n,m=map(int,input().split())
templ=[0]*m
temp=[]
ans=0
for i in range(0,m):
  a,b=map(int,input().split())
  templ[i]=[a,b]
  if a==1:
    if b==n:
      print("POSSIBLE")
      ans=1
      break
    else:
      temp.append([b,n])
if len(temp)>=1 and ans==0:
  c = [x for x in temp if x in templ]
  if len(c)>=1:
    print("POSSIBLE")
  else:
    print("IMPOSSIBLE")
else:
  print("IMPOSSIBLE")            
    

Fixed submission:
n,m=map(int,input().split())
templ=[0]*m
temp=[]
tempb=[]
ans=0
for i in range(0,m):
  a,b=map(int,input().split())
  templ[i]=[a,b]
  if a==1:
    if b==n:
      print("POSSIBLE")
      ans=1
      break
    else:
      temp.append(b)
  if b==n:
    tempb.append(a)
if len(temp)>=1 and ans==0:
  temp=set(temp)
  tempb=set(tempb)
  c = temp&tempb
  #c = [x for x in temp if x in tempb]
  if len(c)>=1:
    print("POSSIBLE")
  else:
    print("IMPOSSIBLE")
  """
  for i in range(0,len(tempb)):
    if tempb[i] in temp:
      print("POSSIBLE")
      break
  """
else:
  print("IMPOSSIBLE")

Buggy python submission (verdict: Time Limit Exceeded):
n,m=map(int,input().split())
templ=[0]*m
temp=[]
ans=0
for i in range(0,m):
  a,b=map(int,input().split())
  templ[i]=[a,b]
  if a==1:
    if b==n:
      print("POSSIBLE")
      ans=1
      break
    else:
      temp.append(b)
if len(temp)>=1 and ans==0:
  for i in range(0,m):
    if templ[i][0] in temp:
      if templ[i][1]==n:
        print("POSSIBLE")
        break
  else:
    print("IMPOSSIBLE")
else:
  print("IMPOSSIBLE")            
    

Fixed submission:
n,m=map(int,input().split())
templ=[0]*m
temp=[]
tempb=[]
ans=0
for i in range(0,m):
  a,b=map(int,input().split())
  templ[i]=[a,b]
  if a==1:
    if b==n:
      print("POSSIBLE")
      ans=1
      break
    else:
      temp.append(b)
  if b==n:
    tempb.append(a)
if len(temp)>=1 and ans==0:
  temp=set(temp)
  tempb=set(tempb)
  c = temp&tempb
  #c = [x for x in temp if x in tempb]
  if len(c)>=1:
    print("POSSIBLE")
  else:
    print("IMPOSSIBLE")
  """
  for i in range(0,len(tempb)):
    if tempb[i] in temp:
      print("POSSIBLE")
      break
  """
else:
  print("IMPOSSIBLE")

Buggy python submission (verdict: Runtime Error):
n,m=map(int,input().split())
temp=[]
for i in range(0,m):
  a,b=map(int,input().split()):
    if a==1:
      if b==n:
        print("POSSIBLE")
        break
      else:
        temp.append(b)
else:
  for i in range(0,len(b)):
    if temp[i]==n:
        print("POSSIBLE")

else:
  print("IMPOSSIBLE")      
    

Fixed submission:
n,m=map(int,input().split())
templ=[0]*m
temp=[]
tempb=[]
ans=0
for i in range(0,m):
  a,b=map(int,input().split())
  templ[i]=[a,b]
  if a==1:
    if b==n:
      print("POSSIBLE")
      ans=1
      break
    else:
      temp.append(b)
  if b==n:
    tempb.append(a)
if len(temp)>=1 and ans==0:
  temp=set(temp)
  tempb=set(tempb)
  c = temp&tempb
  #c = [x for x in temp if x in tempb]
  if len(c)>=1:
    print("POSSIBLE")
  else:
    print("IMPOSSIBLE")
  """
  for i in range(0,len(tempb)):
    if tempb[i] in temp:
      print("POSSIBLE")
      break
  """
else:
  print("IMPOSSIBLE")