n, m = map(int, input().split())
edges = {node: set() for node in range(n)} 
abs_nodes = set()
for _ in range(m):
    smaller, larger = sorted(map(int, input().split()))
    edges[larger].add(smaller)
for node in range(n-1, -1, -1):
    if node in abs_nodes:
        continue
    abs_nodes |= edges[node]
ans = 0
for node in abs_nodes:
    ans |= 1 << node 
print(format(ans, 'b'))