#include<iostream>
#include<fstream>
#include<algorithm>
#include<cstring>
#include<vector>
#include<string>
#include<queue>
#include<cstdlib>
#include<ctime>
#include<map>
#define in cin
#define out cout
#define FOR(i, a, b) for(int i = a; i <= b; ++i)
using namespace std;
typedef long long ll;
const int INF = 0x3f3f3f3f;
const int Nmax = 100001;
vector<int> G[Nmax],Gt[Nmax],C[Nmax],Comp[Nmax];
int N,M,K,m[Nmax],f[Nmax];
int X[3*Nmax],Y[3*Nmax],Cost[3*Nmax];
void dfs1(int x){m[x]=1;for(vector<int>::iterator it=G[x].begin();it!=G[x].end();++it) if(!m[*it]) dfs1(*it);f[++f[0]]=x;}
void dfs2(int x){Comp[K].push_back(x);m[x]=1;for(vector<int>::iterator it=Gt[x].begin();it!=Gt[x].end();++it) if(!m[*it]) dfs2(*it);}
int pof[Nmax],est[Nmax];
int inq[Nmax],D[Nmax],Much[Nmax];
int Tat[Nmax];
queue<int> q;
int c_n(int p,int much){
    while(!q.empty()) q.pop();
    q.push(p); inq[p]=1; D[p]=0;
    while(!q.empty()){
        int x=q.front(); q.pop(); inq[x]=-inq[x];
        for(int i=0;i<G[x].size();i++){
            if(D[x]+C[x][i] < D[G[x][i]]){
                D[G[x][i]]=D[x]+C[x][i];
                if(inq[G[x][i]]<1){
                    if(inq[G[x][i]]<-much){
                        return 1;
                    }
                    q.push(G[x][i]);
                    inq[G[x][i]]=1-inq[G[x][i]];
                }
            }
        }
    }
    return 0;
}
int main(){
    #ifndef ONLINE_JUDGE
    ifstream in("test.in");
    ofstream out("test.out");
    #endif
    in>>N>>M;
    for(int i=1;i<=M;i++){
        in>>X[i]>>Y[i]>>Cost[i];
        G[X[i]].push_back(Y[i]);
        Gt[Y[i]].push_back(X[i]);
    }
    for(int i=1;i<=N;i++) if(!m[i]) dfs1(i);
    for(int i=1;i<=N;i++) m[i]=0;
    for(int i=N;i>=1;i--) if(!m[f[i]]) K++,dfs2(f[i]);

    for(int i=1;i<=K;i++) for(vector<int>::iterator it=Comp[i].begin();it!=Comp[i].end();++it) pof[*it]=i;
    for(int i=1;i<=N;i++) m[i]=0,D[i]=INF,G[i].clear();
    for(int i=1;i<=M;i++){
        if(pof[X[i]]==pof[Y[i]]){
            G[X[i]].push_back(Y[i]);
            C[X[i]].push_back(Cost[i]);
            Much[pof[X[i]]]++;
        }
    }
    for(int i=1;i<=K;i++){
        est[i]=c_n(Comp[i].back(),Much[i]);
    }
    for(int i=1;i<=N;i++) G[i].clear();
    for(int i=1;i<=M;i++){
        if(pof[X[i]]!=pof[Y[i]]){
            G[pof[Y[i]]].push_back(pof[X[i]]);
            Tat[pof[X[i]]]++;
        }
    }
    while(!q.empty()) q.pop();
    for(int i=1;i<=K;i++) if(!Tat[i]) q.push(i);
    while(!q.empty()){
        int x=q.front(); q.pop(); inq[x]=-inq[x];
        for(int i=0;i<G[x].size();i++){
            est[G[x][i]]|=est[x];
            Tat[G[x][i]]--;
            if(Tat[G[x][i]]==0) q.push(G[x][i]);
        }
    }
    int ans=0;
    for(int i=1;i<=K;i++) ans+=est[i]*Comp[i].size();
    out<<ans<<'\n';
    return 0;
}