#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <climits>
#include <cmath>
#include <complex>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <vector>
#include <stack>
using namespace std;
#define int long long
#define mp make_pair
#define fi first
#define pii pair<int,int>
#define se second
const int INF=1000000000000000000;
const int N=200000;
const int M=998244353;
const int ln=20;
struct Mint{
int n;
Mint(int nn){
n=nn%M;
}
Mint(){
n=0;
}
Mint& operator+=(Mint const& m){
n=(n+m.n)%M;
return *this;
}
Mint& operator*=(Mint const& m){
n=(n*m.n)%M;
return *this;
}
Mint& operator-=(Mint const& m){
n=(n+M-m.n)%M;
return *this;
}
friend Mint binpow(Mint a,int b){
if(b==0) return Mint(1);
Mint r=binpow(a,b/2LL);
r*=r;
if(b%2==0) return r;
r*=a;
return r;
}
friend Mint inverse(Mint a){
return binpow(a,M-2);
}
Mint& operator/=(Mint const &b){
return (*this)*=inverse(b);
}
friend Mint operator+(Mint a,Mint const b){
return (a+=b);
}
friend Mint operator-(Mint a,Mint const b){
return (a-=b);
}
friend Mint operator*(Mint a,Mint const b){
return (a*=b);
}
friend Mint operator/(Mint a,Mint const b){
return (a/=b);
}
friend Mint operator-(Mint a){
return 0-a;
}
friend std::ostream& operator<<(std::ostream& os, Mint const& a){
return os << a.n;
}
friend std::istream& operator>>(std::istream& is, Mint& a){
return (is >> a.n);
}
friend bool operator==(Mint const& a,Mint const& b){
return a.n==b.n;
}
friend bool operator!=(Mint const& a,Mint const& b){
return a.n!=b.n;
}
};
template<typename T>
std::ostream& operator<< (std::ostream& os,pair<T,T> p){
return os << p.fi << " " << p.se << "\n";
}
void solve(){
int n,m;
cin >> n >> m;
vector<int> edges[n];
int indeg[n];
for(int i=0;i<n;i++) indeg[i]=0;
for(int i=0;i<m;i++){
int u,v;
cin >> u >> v;
u--,v--;
edges[u].push_back(v);
indeg[v]++;
}
queue<int> q;
for(int i=0;i<n;i++) if(indeg[i]==0) q.push(i);
int cnt=0;
stack<int> s;
while(!q.empty()){
int u=q.front();
q.pop();
s.push(u);
cnt++;
for(int v:edges[u]){
indeg[v]--;
if(indeg[v]==0) q.push(v);
}
}
if(cnt!=n){
cout << -1;
return;
}
while(!s.empty()){
cout << s.top()+1 << " " << 0 << "\n";
s.pop();
}
}
signed main(){
auto begin = std::chrono::high_resolution_clock::now();
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int t;
//cin >> t;
t=1;
while(t--) solve();
auto end = std::chrono::high_resolution_clock::now();
auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n";
}
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