import sys
input = sys.stdin.readline
sys.setrecursionlimit(2*10**5)

class SCC:

    def __init__(self, n):
        self.n = n
        self.graph = [[] for i in range(n)]
        self.graph_rev = [[] for i in range(n)]
        self.used = [False]*n

    def add_edge(self, fr, to):
        if fr == to:
            return
        self.graph[fr].append(to)
        self.graph_rev[to].append(fr)

    def dfs(self, node, graph):
        self.used[node] = True
        for nex in graph[node]:
            if self.used[nex]:
                continue
            self.dfs(nex,graph)
        self.order.append(node)

    def first_dfs(self):
        self.used = [False]*self.n
        self.order = []
        for i in range(self.n):
            if self.used[i]:
                continue
            self.dfs(i,self.graph)
    
    def second_dfs(self):
        self.used = [False]*self.n
        self.ans = []
        for node in reversed(self.order):
            if self.used[node]:
                continue
            self.used[node] = True
            self.order = []
            self.dfs(node, self.graph_rev)
            self.ans.append(self.order)

    def scc(self):
        self.first_dfs()
        self.second_dfs()
        return self.ans


class Unionfind:
     
    def __init__(self,n):
        self.uf = [-1]*n
 
    def find(self,x):
        if self.uf[x] < 0:
            return x
        else:
            self.uf[x] = self.find(self.uf[x])
            return self.uf[x]
 
    def same(self,x,y):
        return self.find(x) == self.find(y)
 
    def union(self,x,y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return False
        if self.uf[x] > self.uf[y]:
            x,y = y,x
        self.uf[x] += self.uf[y]
        self.uf[y] = x
        return True
 
    def size(self,x):
        x = self.find(x)
        return -self.uf[x]

n,m = map(int,input().split())
uf = Unionfind(n)
scc = SCC(n)

for _ in range(m):
    u,v = map(int,input().split())
    u,v = u-1,v-1
    uf.union(u,v)
    scc.add_edge(u,v)

group = scc.scc()
group.append([])
ans = []
for x,y in zip(group,group[1:]):
    if len(x) != 1:
        for i in range(len(x)):
            a = x[i]
            b = x[(i+1)%len(x)]
            ans.append((a,b))
    if y == []:
        continue
    if uf.same(x[0],y[0]):
        ans.append((x[0],y[0]))
print(len(ans))
for x,y in ans:
    print(x+1,y+1)