#include<bits/stdc++.h>
using namespace std;
int N, M, l[100009], r[100009], c[100009];
long long maxA, sumC, b[200009], a[200009], aib[200009];
vector < pair < int, int > > v[200009];
void U (int pos, int val)
{
while (pos <= N)
aib[pos] += val,
pos += pos - (pos & (pos - 1));
}
long long Q (int pos)
{
long long sum = 0;
while (pos)
sum += aib[pos],
pos &= pos - 1;
return sum;
}
bool getVerdict (long long S, long long cntFlipped)
{
if (cntFlipped > sumC) return 0;
for (int i=1; i<=N; i++)
{
long long newA = a[i] + cntFlipped;
if (newA < S) b[i] = 0;
else b[i] = (newA + 1 - S) / 2;
}
for (int i=1; i<=N; i++)
aib[i] = 0;
long long used = 0;
priority_queue < pair < int, int > > PQ;
for (int i=1; i<=N; i++)
{
for (auto r : v[i])
PQ.push (r);
long long needed = max (0LL, b[i] - Q (N - i + 1));
while (!PQ.empty ())
{
auto curr = PQ.top ();
PQ.pop ();
long long f = min (needed, (long long) curr.second);
used += f, needed -= f;
U (N - curr.first + 1, +f);
if (f != curr.second)
PQ.push ({curr.first, curr.second - f});
if (needed == 0)
break;
}
if (needed > 0) return 0;
}
return (used <= cntFlipped);
}
bool ok (long long S)
{
if (S >= maxA) return 1;
if (getVerdict (S, maxA - S)) return 1;
if (getVerdict (S, maxA - S + 1)) return 1;
return 0;
}
int main ()
{
//freopen ("input", "r", stdin);
//freopen ("output", "w", stdout);
scanf ("%d %d", &N, &M);
///N links: 1-2, 2-3, .., N-1
for (int i=1; i<=M; i++)
{
scanf ("%d %d %d", &l[i], &r[i], &c[i]), sumC += c[i];
if (l[i] > r[i]) swap (l[i], r[i]);
a[l[i]] += c[i], a[r[i]] -= c[i];
v[l[i]].push_back ({r[i] - 1, c[i]});
}
long long p = 1, u = 0, mij, ras;
for (int i=1; i<=N; i++)
a[i] += a[i - 1], u = max (u, a[i]);
maxA = u;
while (p <= u)
{
mij = (p + u) >> 1;
if (ok (mij)) ras = mij, u = mij - 1;
else p = mij + 1;
}
printf ("%lld\n", ras);
return 0;
}
