#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>

#define ll long long
#define pb push_back
#define f first
#define s second
#define sz(x) (int)(x).size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define ios ios_base::sync_with_stdio(false);cin.tie(NULL)
#define ld long double
#define li __int128

using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>; ///find_by_order(),order_of_key()
template<int D, typename T>struct vec : public vector<vec<D - 1, T>> {template<typename... Args>vec(int n = 0, Args... args) : vector<vec<D - 1, T>>(n, vec<D - 1, T>(args...)) {}};
template<typename T>struct vec<1, T> : public vector<T> {vec(int n = 0, T val = T()) : vector<T>(n, val) {}};
template<class T1,class T2> ostream& operator<<(ostream& os, const pair<T1,T2>& a) { os << '{' << a.f << ", " << a.s << '}'; return os; }
template<class T> ostream& operator<<(ostream& os, const vector<T>& a){os << '{';for(int i=0;i<sz(a);i++){if(i>0&&i<sz(a))os << ", ";os << a[i];}os<<'}';return os;}
template<class T> ostream& operator<<(ostream& os, const deque<T>& a){os << '{';for(int i=0;i<sz(a);i++){if(i>0&&i<sz(a))os << ", ";os << a[i];}os<<'}';return os;}
template<class T> ostream& operator<<(ostream& os, const set<T>& a) {os << '{';int i=0;for(auto p:a){if(i>0&&i<sz(a))os << ", ";os << p;i++;}os << '}';return os;}
template<class T> ostream& operator<<(ostream& os, const set<T,greater<T> >& a) {os << '{';int i=0;for(auto p:a){if(i>0&&i<sz(a))os << ", ";os << p;i++;}os << '}';return os;}
template<class T> ostream& operator<<(ostream& os, const multiset<T>& a) {os << '{';int i=0;for(auto p:a){if(i>0&&i<sz(a))os << ", ";os << p;i++;}os << '}';return os;}
template<class T> ostream& operator<<(ostream& os, const multiset<T,greater<T> >& a) {os << '{';int i=0;for(auto p:a){if(i>0&&i<sz(a))os << ", ";os << p;i++;}os << '}';return os;}
template<class T1,class T2> ostream& operator<<(ostream& os, const map<T1,T2>& a) {os << '{';int i=0;for(auto p:a){if(i>0&&i<sz(a))os << ", ";os << p;i++;}os << '}';return os;}
int ri(){int x;scanf("%i",&x);return x;}
void rd(int&x){scanf("%i",&x);}
void rd(long long&x){scanf("%lld",&x);}
void rd(double&x){scanf("%lf",&x);}
void rd(long double&x){scanf("%Lf",&x);}
void rd(string&x){cin>>x;}
void rd(char*x){scanf("%s",x);}
template<typename T1,typename T2>void rd(pair<T1,T2>&x){rd(x.first);rd(x.second);}
template<typename T>void rd(vector<T>&x){for(T&p:x)rd(p);}
template<typename C,typename...T>void rd(C&a,T&...args){rd(a);rd(args...);}
//istream& operator>>(istream& is,__int128& a){string s;is>>s;a=0;int i=0;bool neg=false;if(s[0]=='-')neg=true,i++;for(;i<s.size();i++)a=a*10+s[i]-'0';if(neg)a*=-1;return is;}
//ostream& operator<<(ostream& os,__int128 a){bool neg=false;if(a<0)neg=true,a*=-1;ll high=(a/(__int128)1e18);ll low=(a-(__int128)1e18*high);string res;if(neg)res+='-';if(high>0){res+=to_string(high);string temp=to_string(low);res+=string(18-temp.size(),'0');res+=temp;}else res+=to_string(low);os<<res;return os;}

const int N=2005,M=3005;
vector<pair<pair<int,int>,pair<int,int>>> edges;
vector<int> inside(M);
vector<int> par(N);
int find(int tr){return par[tr]==tr?tr:par[tr]=find(par[tr]);}
bool merge(int a,int b){
	a=find(a);
	b=find(b);
	if(a==b){
		return 0;
	}
	par[a]=b;
	return 1;
}
void resetDsu(){
	iota(all(par),0);
}
vector<set<int>> graf(N);
vector<int> rc;
vector<bool> visited(N);
void dfs(int tr){
	visited[tr]=1;
	rc.pb(tr);
	for(auto p:graf[tr]){
		if(!visited[p]){
			dfs(p);
		}
	}
}
int main()
{
	int n=ri(),m=ri();
	for(int i=0;i<m;i++){
		int u=ri()-1,v=ri()-1,w=ri();
		edges.pb({{w,i},{u,v}});
	}
	sort(all(edges));
	resetDsu();
	for(int i=0;i<m;i++){
		if(merge(edges[i].s.f,edges[i].s.s)){
			inside[i]=1;
		}
		else{
			inside[i]=0;
		}
	}
	resetDsu();
	vector<pair<int,pair<int,int>>> outside;
	vector<bool> takenOut;
	vector<pair<int,pair<int,int>>> toReplace;
	for(int i=0;i<m;i++){
		if(inside[i]){
			if(edges[i].f.s>=n-1){
				outside.pb({edges[i].f.s,{edges[i].s}});
				takenOut.pb(0);
			}
			else{
				graf[edges[i].s.f].insert(edges[i].s.s);
				graf[edges[i].s.s].insert(edges[i].s.f);
			}
		}
		else{
			if(edges[i].f.s<n-1){
				toReplace.pb({edges[i].f.s,{edges[i].s}});
				graf[edges[i].s.f].insert(edges[i].s.s);
				graf[edges[i].s.s].insert(edges[i].s.f);
			}
		}
	}
	printf("%i\n",sz(toReplace));
	for(auto p:toReplace){
		int i=p.f;
		graf[p.s.f].erase(p.s.s);
		graf[p.s.s].erase(p.s.f);
		dfs(p.s.s);
		bool found=0;
		for(int i=0;i<sz(outside);i++){
			if(takenOut[i]){
				continue;
			}
			if(((int)visited[outside[i].s.f]^(int)visited[outside[i].s.s])==1){
				found=1;
				takenOut[i]=1;
				graf[outside[i].s.f].insert(outside[i].s.s);
				graf[outside[i].s.s].insert(outside[i].s.f);
				printf("%i %i\n",i+1,outside[i].f+1);
				break;
			}
		}
		assert(found);
		for(auto p:rc){
			visited[p]=0;
		}
		rc.clear();
	}
	return 0;
}