样例输入：
5 12
1 5 5
3 4 10
4 10 6
11 12 5
10 12 3
样例输出
3
样例输入：
1 10
1 10 23
样例输出
0
#define mid ((l + r) >> 1)
int t[maxn], tg[maxn];
struct seg {
int l, r, w;
bool friend operator <(seg a, seg b){
return a.w < b.w;
}
} seg[maxn];
int n, m;
void Modify(int rt, int l, int r, int L, int R, int val)
{
if (l >= L && r <= R) {
t[rt] += val;
tg[rt] += val;
return;
}
if (L <= mid) Modify(rt << 1, l, mid, L, R, val);
if (R > mid) Modify(rt << 1 | 1, mid + 1, r, L, R, val);
t[rt] = tg[rt] + min(t[rt << 1], t[rt << 1 | 1]);
return;
}
int main()
{
n = read, m = read;
for (int i = 1; i <= n; i++) {
seg[i].l = read, seg[i].r = read, seg[i].w = read;
}
sort(seg + 1, seg + 1 + n);
int l = 1, ans = 1 << 30;
for (int r = 1; r <= n; r++) {
Modify(1, 1, m - 1, seg[r].l, seg[r].r - 1, 1);
while (t[1]) {
ans = min(ans, seg[r].w - seg[l].w);
Modify(1, 1, m - 1, seg[l].l, seg[l].r - 1, -1);
l++;
}
}
cout << ans << endl;
return 0;
}
/**
**/