#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cassert>
#include <queue>
using ll = long long;
int const nmax = 200000;
ll acc[5 + nmax];
ll init[5 + nmax], pref[5 + nmax], suff[5 + nmax];
std::vector<std::pair<int,int>> queries[5 + nmax];
bool solve(int n, int m, int start, ll smax, ll target) {
std::priority_queue<std::pair<int,int>> pq;
for(int i = 1;i <= n; i++)
acc[i] = 0;
ll expended = 0;
for(int i = 1;i <= start; i++) {
ll needToErase = (1 + init[i] + target - smax) / 2;
needToErase = std::max(0LL, needToErase - expended);
for(int h = 0; h < queries[i].size(); h++)
pq.push(queries[i][h]);
expended += needToErase;
while(0 < pq.size() && 0 < needToErase) {
std::pair<int,int> tp = pq.top();
pq.pop();
if(needToErase < tp.second) {
tp.second -= needToErase;
pq.push(tp);
acc[start] -= needToErase;
acc[tp.first + 1] += 2 * needToErase;
needToErase = 0;
} else {
acc[start] -= tp.second;
acc[tp.first + 1] += 2 * tp.second;
needToErase -= tp.second;
}
}
if(0 < needToErase)
return 0;
}
for(int i = 1; i <= n; i++)
acc[i] += acc[i - 1];
for(int i = start;i <= n; i++)
if(!(acc[i] + init[i] <= smax))
return 0;
return 1;
};
int main() {
std::ios::sync_with_stdio(0);
std::cin.tie(0);
int n, m;
std::cin >> n >> m;
for(int i = 1;i <= m; i++) {
int x, y, cost;
std::cin >> x >> y >> cost;
if(y < x)
std::swap(x, y);
y--;
queries[x].push_back({y, cost});
init[x] += cost;
init[y + 1] -= cost;
}
for(int i = 2;i <= n; i++)
init[i] += init[i - 1];
int start = 1;
for(int i = 1; i <= n; i++)
if(init[start] < init[i])
start = i;
ll x = 0;
for(ll jump = (1LL << 60); 0 < jump; jump /= 2)
if(solve(n, m, start, init[start] - (x + jump), x + jump) == 1 || solve(n, m, start, init[start] - (x + jump), x + jump + 1))
x += jump;
std::cout << init[start] - x << '\n';
return 0;
}
