#pragma GCC optimize("O3") #pragma GCC target ("avx2") #include<bits/stdc++.h> using namespace std; using ll=long long; using P=pair<ll,ll>; template<class T> using V=vector<T>; #define fi first #define se second #define all(v) (v).begin(),(v).end() const ll inf=(1e18); //const ll mod=998244353; const ll mod=1000000007; ll GCD(ll a,ll b) {return b ? GCD(b,a%b):a;} ll LCM(ll c,ll d){return c/GCD(c,d)*d;} struct __INIT{__INIT(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(20);}} __init; template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; } template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; } template<class T>void debag(const vector<T> &a){cerr<<"debag :";for(auto v:a)cerr<<v<<" ";cerr<<"\n";} template<class T>void print(const vector<T> &a){for(auto v:a)cout<<v<<" ";cout<<"\n";} int main(){ ll n,d; cin>>n>>d; ll l=-(1e10),r=(1e10); V<ll> p(n),q(n); for(int i=0;i<n;i++)cin>>p[i]>>q[i]; while(r-l>1){ ll a=0,ab=-1,b=-inf,bb=-1; ll mid=(l+r)/2; for(int i=0;i<d;i++){ ll na=-inf,nb=-inf,nab=-1,nbb=-1,nc=-inf,ncb=-1; for(int j=0;j<n;j++){ if(a-p[j]>=mid&&ab!=j){ if(na<a-p[j]+q[j]){ nc=nb; ncb=nbb; nb=na; nbb=nab; nab=j; na=a-p[j]+q[j]; }else if(nb<a-p[j]+q[j]){ nc=nb; ncb=nbb; nbb=j; nb=a-p[j]+q[j]; }else if(nc<a-p[j]+q[j]){ ncb=j; nc=a-p[j]+q[j]; } } if(b-p[j]>=mid&&bb!=j){ if(na<b-p[j]+q[j]){ nc=nb; ncb=nbb; nb=na; nbb=nab; nab=j; na=b-p[j]+q[j]; }else if(nb<b-p[j]+q[j]){ nc=nb; ncb=nbb; nbb=j; nb=b-p[j]+q[j]; }else if(nc<b-p[j]+q[j]){ ncb=j; nc=b-p[j]+q[j]; } } } a=na;ab=nab; if(nab==nbb){ b=nc; bb=ncb; }else{ b=nb; bb=nbb; } } if(a>=mid)l=mid; else r=mid; } cout<<l<<"\n"; }