#include <bits/stdc++.h>
using namespace std;
const int maxn = 200005, inf = 1000000000;
int n, m, i, j;
struct data {
  int h, l, r;
  bool operator<(const data& t) const { return h < t.h; }
} d[maxn];
int Hs[maxn], dp[maxn], tot;
int mark[maxn << 2];
int ll, rr, nam;
void calc() {
  if (nam == -1) return;
  if (min(d[i].r, d[nam].r) - max(d[i].l, d[nam].l) > Hs[rr] - Hs[ll - 1])
    return;
  dp[i] = max(dp[i], min(dp[nam], Hs[rr] - Hs[ll - 1]));
}
void cal(int x, int l, int r, int L, int R) {
  if (~mark[x]) {
    if (mark[x] != nam) {
      calc();
      nam = mark[x];
      ll = L;
    }
    rr = R;
    return;
  }
  int mid = (l + r) >> 1;
  if (R <= mid)
    cal(x << 1, l, mid, L, R);
  else if (L > mid)
    cal(x << 1 | 1, mid + 1, r, L, R);
  else
    cal(x << 1, l, mid, L, mid), cal(x << 1 | 1, mid + 1, r, mid + 1, R);
}
void upd(int x, int l, int r, int L, int R) {
  if (L <= l && r <= R) {
    mark[x] = i;
    return;
  }
  if (mark[x] != -1) {
    mark[x << 1] = mark[x << 1 | 1] = mark[x];
    mark[x] = -1;
  }
  int mid = (l + r) >> 1;
  if (L <= mid) upd(x << 1, l, mid, L, R);
  if (R > mid) upd(x << 1 | 1, mid + 1, r, L, R);
}
void build(int x, int l, int r) {
  if (l == r) return;
  mark[x] = -1;
  int mid = (l + r) >> 1;
  build(x << 1, l, mid);
  build(x << 1 | 1, mid + 1, r);
}
int main() {
  scanf("%d%d", &n, &m);
  for (i = 1; i <= n; i++)
    scanf("%d%d%d", &d[i].h, &d[i].l, &d[i].r), Hs[++tot] = d[i].l,
                                                Hs[++tot] = d[i].r;
  Hs[++tot] = inf;
  Hs[++tot] = -inf;
  sort(Hs + 1, Hs + tot + 1), tot = unique(Hs + 1, Hs + tot + 1) - Hs - 1;
  sort(d + 1, d + n + 1);
  d[0].l = d[n + 1].l = -inf;
  d[0].r = d[n + 1].r = inf;
  dp[0] = 2 * inf;
  build(1, 1, n);
  for (i = 1; i <= n + 1; i++) {
    int l = lower_bound(Hs + 1, Hs + tot + 1, d[i].l) - Hs + 1;
    int r = lower_bound(Hs + 1, Hs + tot + 1, d[i].r) - Hs;
    nam = -1;
    cal(1, 1, tot, l, r);
    calc();
    upd(1, 1, tot, l, r);
  }
  printf("%d\n", dp[n + 1]);
  return 0;
}
