#include <bits/stdc++.h>
using namespace std;
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define sz(a) (int)(a).size()
#define all(a) (a).begin(), (a).end()
#define bit(s, i) (((s) >> (i)) & 1)
#define ii pair <int, int>
#define fi first
#define se second
#define ll long long
#define eb emplace_back
#define pb push_back
#define __builtin_popcount __builtin_popcountll
template <class X, class Y>
bool maximize(X &x, Y y) {
if(x < y) {
x = y;
return true;
}
return false;
}
template <class X, class Y>
bool minimize(X &x, Y y) {
if(x > y) {
x = y;
return true;
}
return false;
}
void solve();
int32_t main() {
#define task "test"
if(fopen(task".inp", "r")){
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
cin.tie(0)->sync_with_stdio(0);
int tc = 1; //cin >> tc;
FOR(i, 1, tc){
solve();
}
}
const int N=2e5+5;
int n,m,p; ll a[N],s[N],tot;
vector<ii> seg[N];
priority_queue<ii> pq;
bool chk(ll mxB, ll M){
FOR(i,1,n) s[i]=0;
while(!pq.empty()) pq.pop();
ll cur=0;
FOR(i,1,p){
ll need=(a[i]+mxB-M+1)/2;
for(auto [x,y]:seg[i]){
if(x>p){
pq.push({x,y});
}
}
while(cur<need){
if(pq.empty()) return false;
auto [x,y]=pq.top(); pq.pop();
if(cur+y<=need){
cur+=y;
s[x]+=y;
}
else{
s[x]+=need-cur;
pq.push({x,y-(need-cur)});
cur=need;
}
}
}
FOR(i,p+1,n){
cur-=s[i];
ll need=(a[i]+mxB-M+1)/2;
if(cur<need) return false;
}
return true;
}
void solve() {
cin>>n>>m;
FOR(i,1,m){
int l,r,c; cin>>l>>r>>c;
if(l>r) swap(l,r);
a[l]+=c; a[r]-=c;
seg[l].eb(r,c);
tot+=c;
}
p=1;
FOR(i,1,n){
a[i]+=a[i-1];
if(a[i]>a[p]) p=i;
}
ll L=1, R=tot, res=0;
while(L<=R){
ll M=(L+R)>>1;
if(chk(a[p]-M,M)||chk(a[p]-M+1,M)){
res=M;
R=M-1;
}
else{
L=M+1;
}
}
cout<<res<<'\n';
}
