#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'

class dsu {
    public:
    vector<int> p, sz;
    int n, groups;
    dsu(int _n) : n(_n), groups(_n) {
	    p.resize(n);
	    iota(p.begin(), p.end(), 0);
	    sz.assign(n,1);
    }
    int get(int x) {
        return (x == p[x] ? x : (p[x] = get(p[x])));
    }
    bool unite(int x, int y) {
        x = get(x);
        y = get(y);
        if (x != y) {
        	if(sz[x] < sz[y]) swap(x,y);
            p[y] = x;
            sz[x] += sz[y];
            groups--;
            return true;
        }
        return false;
    }
    int size(int x){
    	return sz[get(x)];
    }
};

int main(){
	ios::sync_with_stdio(false); cin.tie(0);
	int n, m;
	cin >> n >> m;
	dsu d(n);
	vector<array<int,4>> a(m);
	for(int i=0; i<m; i++){
	    cin >> a[i][2] >> a[i][3] >> a[i][0];
	    a[i][2]--;
	    a[i][3]--;
	    a[i][1] = i;
	}
	sort(a.begin(), a.end());
	vector<int> res(m);
	for(auto &[_, idx, u, v] : a){
	    if(d.get(u) != d.get(v)){
	        res[idx] = 1;
	        d.unite(u, v);
	    }
	}
	sort(a.begin(), a.end(), [](array<int,4> u, array<int,4> v){
	   return u[1] < v[1]; 
	});
	vector<set<array<int,2>>> adj(n);
	vector<int> rmv, add, used(m);
	vector<array<int,2>> ans;
	for(int i=0; i<m; i++){
	    assert(a[i][1] == i);
	    if(res[i] && i>=n-1) add.push_back(i);
	    if(!res[i] && i<n-1) rmv.push_back(i);
	    if(i<n-1){
	        adj[a[i][2]].insert({i, a[i][3]});
	        adj[a[i][3]].insert({i, a[i][2]});
	    }
	}
	auto remove_edge = [&](int i){
	    assert(adj[a[i][2]].count({i, a[i][3]}));
	    adj[a[i][2]].erase({i, a[i][3]});
	    assert(adj[a[i][3]].count({i, a[i][2]}));
	    adj[a[i][3]].erase({i, a[i][2]});
	};
	auto add_edge = [&](int i){
	    adj[a[i][2]].insert({i, a[i][3]});
	    adj[a[i][3]].insert({i, a[i][2]});
	};
	// For each edge in rmv:
	// Color one set of vertices blue, one set red.
	// Find any edge in add with one blue, one red.
	for(int i : rmv){
	    auto [_, i2, u, v] = a[i];
	    assert(i == i2);
	    vector<int> color(n);
	    function<void(int, int)> dfs = [&](int u, int c){
	        color[u] = c;
	        for(auto &[ei, w] : adj[u]){
	            if(ei == i) continue;
	            if(color[w]) continue;
	            dfs(w, c);
	        }
	    };
	    dfs(u, 1);
	    dfs(v, 2);
	    bool found = 0;
	    for(int j : add){
	        if(used[j]) continue;
	        if(color[a[j][2]] != color[a[j][3]]){
	            assert(color[a[j][2]] + color[a[j][3]] == 3);
	            used[j] = 1;
	            ans.push_back({i, j});
	            remove_edge(i);
	            add_edge(j);
	            found = 1;
	            break;
	        }
	    }
	    assert(found);
	}
	cout << ans.size() << endl;
	for(auto &[u, v] : ans){
	    cout << u+1 << ' ' << v+1 << endl;
	}
}