#include <iostream>

#include <string>

#include <vector>

#include <algorithm>

#include <cstdio>

using namespace std;

#define REP(i,n) for(int i=0;i<(n);++i)

#define FOR(i,a,b) for(int i=(a);i<=(b);++i)

#define RFOR(i,a,b) for(int i=(a);i>=(b);--i)

typedef long long LL;

class player {

int p, e;

};

bool cmp1(const player& a, const player& b) {

return a.p > b.p;

}

bool cmp2(const player& a, const player& b) {

return a.e > b.e;

}

int n, k;

LL sum, res;

vector<player> mm, dd;

void doit(int win) {

int rk = 1;

LL sub = 0;

REP(i,n) {

if (mm[i].p > win) ++rk;

}

int lo = n - win;

REP(i,n) {

if (lo == 0) break;

bool chk = (dd[i].p == win || dd[i].p + 1 == win);

if (chk && rk == k) continue;

if (chk) ++rk;

sub += dd[i].e;

--lo;

}

//if (lo == 0) {

res = min(res, sum - sub);

//}

}

int main() {

scanf("%d %d", &n, &k);

if (k == n + 1) {

printf("0\n");

return 0;

}

sum = 0;

mm.clear();

dd.clear();

REP(i,n) {

player ppl;

scanf("%d %d", &ppl.p, &ppl.e);

mm.push_back(ppl);

dd.push_back(ppl);

sum += ppl.e;

}

sort(mm.begin(), mm.end(), cmp1);

sort(dd.begin(), dd.end(), cmp2);

res = sum;

int W = mm[k - 1].p;

if (W > n) {

printf("-1\n");

return 0;

}

if (W + 2 <= n) doit(W + 2);

if (W + 1 <= n) doit(W + 1);

doit(W);

printf("%I64d\n", res);

return 0;

}