# n = input().strip().split(' ')
#
# obj = {}
#
# for i in range(int(n[1])):
#     a = input().strip().split(' ')
#     if (a[0] in obj) == False:
#         obj[a[0]] = []
#     obj[a[0]].append(a[1])
#
# if ('1' in obj) == True:
#     for i in obj['1']:
#         if (i in obj) == True:
#             for k in obj[i]:
#                 if k == n[0]:
#                     print('POSSIBLE')
#                     break
#         else:
#             print('IMPOSSIBLE')
# else:
#     print('IMPOSSIBLE')


n = input().split(' ')

obj = {}

for i in range(int(n[1])):
    a = input().split(' ')
    if (a[0] in obj) == False:
        obj[a[0]] = []
    obj[a[0]].append(a[1])

def func():
    if ('1' in obj) == True:
        for i in obj['1']:
            if (i in obj) == True:
                for k in obj[i]:
                    if k == n[0]:
                        print('POSSIBLE')
                        return
    print('IMPOSSIBLE')
func()
