#include <cstdio>
#include <algorithm>
const int N = 200000 + 10;
typedef long long i64;
int n, m;
struct Tuple {
int x, y, z;
Tuple() {}
Tuple(int _x, int _y, int _z): x(_x), y(_y), z(_z) {}
inline bool operator< (const Tuple &rhs) const {
return x < rhs.x;
}
} tuple[N];
i64 a[N];
bool solve(i64 cnt, i64 threshold) {
cnt = std::min(cnt, threshold);
static i64 b[N];
std::fill(b + 1, b + n, 0);
static std::pair<int, int> heap[N];
i64 temp = cnt;
int top = 0;
for (int i = 1, j = 1; i < n; ++i) {
b[i] += b[i - 1];
for (; j <= m && tuple[j].x <= i; ++j) {
heap[top++] = std::make_pair(tuple[j].y, tuple[j].z);
std::push_heap(heap, heap + top);
}
i64 val = a[i] + cnt - 2 * b[i] - threshold;
if (val <= 0) continue;
i64 cur = (val + 1) / 2;
while (top && cur && temp) {
std::pop_heap(heap, heap + top);
std::pair<int, int> &info = heap[--top];
if (i >= info.first) continue;
int det = std::min<i64>(info.second, std::min(cur, temp));
info.second -= det;
b[i] += det;
b[info.first] -= det;
cur -= det;
temp -= det;
if (info.second) std::push_heap(heap, heap + ++top);
}
if (cur) return false;
}
return true;
}
int main() {
scanf("%d%d", &n, &m);
for (int i = 1; i <= m; ++i) {
int x, y, z;
scanf("%d%d%d", &x, &y, &z);
if (x > y) std::swap(x, y);
tuple[i] = Tuple(x, y, z);
a[x] += z;
a[y] -= z;
}
std::sort(tuple + 1, tuple + m + 1);
for (int i = 1; i <= n; ++i) a[i] += a[i - 1];
i64 l = 1, t = *std::max_element(a + 1, a + n), r = t;
while (l < r) {
i64 mid = (l + r) >> 1;
if (solve(t - mid, mid) || solve(t - (mid - 1), mid)) r = mid; else l = mid + 1;
}
printf("%lld\n", l);
return 0;
}
