#include<bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
#define pb push_back
#define mp make_pair
typedef pair<int, int> ii;
typedef pair<ii, int> iii;
typedef pair<ii, ii> iiii;
const int N = 3e5 + 5;
const int oo = 1e18 + 7, mod = 1e9 + 7;
int n, k;
int l[N], r[N];
iii seg[N];
int mini[N];
int nxt[N];
int eval[N][21];
bool cook[N];
int le[N], ri[N];
set<ii> seg1[N], seg2[N];
int comp[N];
//int mn_r[N];
int cal(int le, int ri){
int temp = lower_bound(seg + 1, seg + n + 1, make_pair(make_pair(le, -oo), -oo)) - seg;
if(temp == (n + 1)) return 0;
temp = mini[temp];
if(r[temp] > ri) return 0;
int answer = 1;
for(int i = 18; i >= 0; i--){
if(eval[temp][i] == oo) continue;
if(r[eval[temp][i]] <= ri){
answer += (1LL << i);
temp = eval[temp][i];
}
}
return answer;
}
void process(){
cin >> n >> k;
for(int i = 1; i <= n; i++){
cin >> seg[i].fi.fi >> seg[i].fi.se;
seg[i].se = i;
l[i] = seg[i].fi.fi, r[i] = seg[i].fi.se;
}
sort(seg + 1, seg + n + 1);
mini[n + 1] = oo;
for(int i = n; i >= 1; i--){
int temp = lower_bound(seg + 1, seg + n + 1, make_pair(make_pair(seg[i].fi.se, -oo), -oo)) - seg;
if(temp == (n + 1)) nxt[seg[i].se] = oo;
else nxt[seg[i].se] = mini[temp];
mini[i] = mini[i + 1];
if(i == n || seg[i].fi.se <= seg[mini[i]].fi.se) mini[i] = seg[i].se;
eval[seg[i].se][0] = nxt[seg[i].se];
}
for(int i = 1; i <= 18; i++){
for(int j = 1; j <= n; j++){
if(eval[j][i - 1] == oo) eval[j][i] = oo;
else eval[j][i] = eval[eval[j][i - 1]][i - 1];
}
}
le[1] = 0, ri[1] = 1e9;
for(int i = 1; i <= n; i++){
seg1[1].insert({l[i], i});
seg2[1].insert({r[i], i});
comp[i] = 1;
}
int cur = cal(0, 1e9);
//cout << cur << "\n";
if(cur < k){
cout << -1;
return;
}
cur -= k;
int tol_comp = 1;
int num = 0;
for(int i = 1; i <= n; i++){
if(cook[i]) continue;
cook[i] = 1;
//if(l[i] < le[root] || r[i] > ri[root]) continue;
int root = comp[i];
int diff = cal(le[root], ri[root]);
diff -= cal(le[root], l[i]) + cal(r[i], ri[root]) + 1;
//cout << diff << "\n";
assert(diff >= 0);
if(cur < diff){
seg1[comp[i]].erase({l[i], i});
seg2[comp[i]].erase({r[i], i});
// cook[i] = 1;
continue;
}
num++;
cur -= diff;
bool which = 0;
set<ii>::iterator it1 = seg1[root].lower_bound({r[i], -oo}), it2 = seg2[root].lower_bound({l[i] + 1, -oo});
if(it2 == seg2[root].begin()) which = 0;
else{
it2--;
while(1){
if(it1 == seg1[root].end()){
which = 1;
break;
}
if(it2 == seg2[root].begin()){
which = 0;
break;
}
it1++;
it2--;
}
}
if(!which){
tol_comp++;
le[tol_comp] = le[root], ri[tol_comp] = l[i];
le[root] = r[i];
set<ii>::iterator it1 = seg1[root].lower_bound({r[i], -oo}), it2 = seg2[root].lower_bound({l[i] + 1, -oo});
vector<int> er;
if(it2 != seg2[root].begin()){
it2--;
for(;; it2--){
er.pb((*it2).se);
if(it2 == seg2[root].begin()) break;
}
}
for(auto it : er){
comp[it] = tol_comp;
seg1[root].erase({l[it], it});
seg2[root].erase({r[it], it});
seg1[tol_comp].insert({l[it], it});
seg2[tol_comp].insert({r[it], it});
}
er.clear();
it1 = seg1[root].begin();
for(; it1 != seg1[root].end(); it1++){
if((*it1).fi >= r[i]) break;
er.pb((*it1).se);
}
for(auto it : er){
cook[it] = 1;
seg1[root].erase({l[it], it});
seg2[root].erase({r[it], it});
}
}
else{
tol_comp++;
le[tol_comp] = r[i], ri[tol_comp] = ri[root];
ri[root] = l[i];
set<ii>::iterator it1 = seg1[root].lower_bound({r[i], -oo});
vector<int> er;
for(; it1 != seg1[root].end(); it1++){
er.pb((*it2).se);
if(it2 == seg2[root].begin()) break;
}
for(auto it : er){
comp[it] = tol_comp;
seg1[root].erase({l[it], it});
seg2[root].erase({r[it], it});
seg1[tol_comp].insert({l[it], it});
seg2[tol_comp].insert({r[it], it});
}
er.clear();
if(seg2[root].size()){
it1 = seg2[root].end();
it1--;
for(; ; it1--){
if((*it1).fi <= l[i]) break;
er.pb((*it1).se);
if(it1 == seg2[root].begin()) break;
}
for(auto it : er){
cook[it] = 1;
seg1[root].erase({l[it], it});
seg2[root].erase({r[it], it});
}
}
}
cout << i << "\n";
if(num == k) break;
}
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
process();
}
