#include <bits/stdc++.h>
#pragma GCC optimize ("O2,unroll-loops")
//#pragma GCC optimize("no-stack-protector,fast-math")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<pii, int> piii;
typedef pair<ll, ll> pll;
#define debug(x) cerr<<#x<<'='<<(x)<<endl;
#define debugp(x) cerr<<#x<<"= {"<<(x.first)<<", "<<(x.second)<<"}"<<endl;
#define debug2(x, y) cerr<<"{"<<#x<<", "<<#y<<"} = {"<<(x)<<", "<<(y)<<"}"<<endl;
#define debugv(v) {cerr<<#v<<" : ";for (auto x:v) cerr<<x<<' ';cerr<<endl;}
#define all(x) x.begin(), x.end()
#define pb push_back
#define kill(x) return cout<<x<<'\n', 0;
const int inf=1000000010;
const ll INF=1000000000000001000LL;
const int mod=1000000007;
const int MAXN=200010, LOG=17;
int n, m, k, u, v, x, y, t, a, b;
int A[MAXN], B[MAXN], C[MAXN];
ll ps[MAXN], ans, mx;
vector<pii> vec[MAXN];
struct Fenwick{
ll fen[MAXN];
void reset(){
memset(fen, 0, sizeof(fen));
}
void add(int pos, ll val){
for (; pos<MAXN; pos+=pos&-pos) fen[pos]+=val;
}
int get(int pos){
int res=0;
for (; pos; pos-=pos&-pos) res+=fen[pos];
return res;
}
} fen;
bool Check2(ll ted){
fen.reset();
fen.add(1, ted);
for (int i=1; i<n; i++) fen.add(i, ps[i]-ps[i-1]);
priority_queue<pii> pq;
for (int i=1; i<n; i++){
for (pii p:vec[i]) pq.push(p);
ll val=fen.get(i);
while (val>ans){
if (pq.empty()) return 0;
pii p=pq.top();
pq.pop();
int j=p.first;
ll cnt=p.second;
if (j<=i) return 0;
ll t=min((val-ans+1)/2, cnt);
fen.add(i, -2*t);
fen.add(j, +2*t);
val-=2*t;
if (cnt-=t) pq.push({j, cnt});
}
}
return 1;
}
bool Check(){
if (mx<=ans) return 1;
if ((mx+1)/2>ans) return 0;
if (Check2(mx-ans) || Check2(mx-ans+1)) return 1;
return 0;
}
int main(){
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
cin>>n>>m;
for (int i=1; i<=m; i++){
cin>>A[i]>>B[i]>>C[i];
if (A[i]>B[i]) swap(A[i], B[i]);
ps[A[i]]+=C[i];
ps[B[i]]-=C[i];
}
for (int i=1; i<=n; i++) ps[i]+=ps[i-1];
mx=*max_element(ps+1, ps+n);
int l=0, r=0;
for (int i=1; i<n; i++) if (ps[i]==mx){
if (!l) l=i;
r=i;
}
for (int j=1; j<=m; j++) if (A[j]<=l && r<B[j]) vec[A[j]].pb({B[j], C[j]});
ll dwn=0, up=mx;
while (up-dwn>1){
ans=(dwn+up)>>1;
if (Check()) up=ans;
else dwn=ans;
}
cout<<up<<"\n";
return 0;
}
/*
3 3
1 2 1
2 3 1
3 1 1
6 3
1 4 1
2 5 1
3 6 1
*/
