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| #include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define l(x) t[(x)].l
#define r(x) t[(x)].r
#define tag(x) t[(x)].tag
#define res(x) t[(x)].max
using namespace std;
const int MAXN = 5e6 + 10;
struct Segment {
int max;
int l;
int r;
int tag;
}t[MAXN << 3];
struct Interval {
int x, y;
int l;
bool operator < (const Interval &p) {
return l < p.l;
}
}p[MAXN];
int base[MAXN << 1], n, m, cnt;
void build(int p, int x, int y) {
l(p) = x, r(p) = y;
if (x != y) {
int mid = (x + y) >> 1;
build(p << 1, x, mid);
build(p << 1 | 1, mid + 1, y);
}
}
inline void pushdown(int p) {
if (l(p) != r(p) && tag(p) != 0) {
int x = tag(p);
tag(p << 1) += x;
res(p << 1) += x;
tag(p << 1 | 1) += x;
res(p << 1 | 1) += x;
tag(p) = 0;
}
}
void printtree(int p) {
printf("--%d:[%d,%d]--\n", p, l(p), r(p));
printf("max=%d\n", res(p));
printf("tag=%d\n", tag(p));
if (l(p) != r(p)) {
printf("ls: %d, rs: %d\n", p << 1, p << 1 | 1);
printtree(p << 1);
printtree(p << 1 | 1);
}
}
void modify(int p, int x, int y, int val) {
if (x > y) return;
if (x <= l(p) && r(p) <= y) {
tag(p) += val;
res(p) += val;
return;
}
int mid = (l(p) + r(p)) >> 1;
pushdown(p);
if (x <= mid) {
modify(p << 1, x, y, val);
}
if (mid < y) {
modify(p << 1 | 1, x, y, val);
}
res(p) = max(res(p << 1), res(p << 1 | 1));
}
int main() {
scanf("%d%d", &n, &m);
for (int i = 1; i <= n; i++) {
scanf("%d%d", &p[i].x, &p[i].y);
p[i].l = p[i].y - p[i].x;
base[++cnt] = p[i].x;
base[++cnt] = p[i].y;
}
sort(base + 1, base + cnt + 1);
cnt = unique(base + 1, base + cnt + 1) - base - 1;
for (int i = 1; i <= n; i++) {
p[i].x = lower_bound(base + 1, base + cnt + 1, p[i].x) - base;
p[i].y = lower_bound(base + 1, base + cnt + 1, p[i].y) - base;
}
sort(p + 1, p + n + 1);
build(1, 1, cnt);
int pos = 1, ans = 0x3f3f3f3f;
for (int i = 1; i <= n; i++) {
modify(1, p[i].x, p[i].y, 1);
if (res(1) == m) {
ans = min(ans, p[i].l - p[pos].l);
}
while (res(1) == m && pos <= i) {
ans = min(ans, p[i].l - p[pos].l);
if (pos != 0) {
modify(1, p[pos].x, p[pos].y, -1);
}
pos++;
}
}
if (ans != 0x3f3f3f3f)
printf("%d\n", ans);
else
puts("-1");
return 0;
}
|
