n, m = map(int, input().split())

is1 = [False] * (n + 1)
isN = [False] * (n + 1)

for i in range(m):
    a, b = map(int, input().split())
    if(a > b):
        a, b = b, a
    if(a == 1):
        is1[b] = True
    if(b == n):
        isN[a] = True

import sys

for i in range(2, n):
    if(is1[i] and isN[i]):
        print("POSSIBLE")
        sys.exit(0)

print("IMPOSSIBLE")
