#include <bits/stdc++.h>

using namespace std;
#define int long long
#define app push_back
#ifndef LOCAL
#define endl '\n'
#endif // LOCAL
typedef long long ll;
struct Line {
    ll k, b;

    Line() : k(), b() {}
    Line (ll _k, ll _b) : k(_k), b(_b) {}

    ll getVal(ll x) {
        return k * x + b;
    }
};
ll div_up(ll a, ll b) { return a/b+((a^b)>0&&a%b); } // divide a by b rounded up
struct Hull {
    vector<Line> lines;
    vector<ll> borders;

    Hull() : lines(), borders() {}

    void addLine(Line L) {
        while(!lines.empty()) {
            if (lines.back().getVal(borders.back()) >= L.getVal(borders.back())) {
                lines.pop_back();
                borders.pop_back();
            } else break;
        }
        if (lines.empty()) {
            lines.push_back(L);
            borders.push_back(0LL); //leftmost query
            return;
        }
        if (lines.back().k <= L.k) return;
        ll x = div_up(L.b - lines.back().b, lines.back().k - L.k); //must work for negative!
        lines.push_back(L);
        borders.push_back(x);
    }
    ll getMinVal(ll x) {
        int pos = upper_bound(borders.begin(), borders.end(), x) - borders.begin();
        if (pos == 0) throw;
        pos--;
        return lines[pos].getVal(x);
    }
};
Hull c;
vector<int> slv1(vector<pair<int,int> > a,int m)
{
    set<pair<int,int> > d;
    vector<int> answ={0};
    if(a.empty()) {for(int i=0;i<m;++i) answ.push_back(-1e18); return answ;}
    for(int i=0;i<a.size();++i) {d.insert({a[i].first,i});}
    for(int i=0;i<m;++i)
    {
        auto o=*--d.end();d.erase(o);
        answ.push_back(answ.back()+o.first);
        o.first+=a[o.second].second;d.insert(o);
    }
    return answ;
}
vector<int> slv2(vector<pair<int,int> > v,int m)
{
    if(v.empty()) {vector<int> answ;for(int i=0;i<=m;++i) answ.push_back((i!=0)*(-1e18)); return answ;}
    vector<pair<int,int> > l;
    for(auto [a,d]:v)
    {
        l.push_back({-d,-2*a+d});
    }
    sort(l.begin(),l.end());reverse(l.begin(),l.end());
    for(auto [k,b]:l)
    {
        c.addLine(Line(k,b));
    }
    vector<int> res;
    for(int i=0;i<=m;++i)
    {
        int ans=-c.getMinVal(i);
        ans*=i;assert(ans%2==0);ans/=2;
        res.push_back(ans);
    }
    return res;
}
int32_t main()
{
    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    int n,m;cin>>n>>m;
    vector<pair<int,int> > v1,v2;
    for(int i=0;i<n;++i) {int x,y;cin>>x>>y;if(y<=0) {v1.push_back({x,y});} else {v2.push_back({x,y});}}
    vector<int> res1=slv1(v1,m);vector<int> res2=slv2(v2,m);
    //for(int x:res1) cout<<x<<' '; cout<<endl;
    int answ=(-1e18);
    for(int i=0;i<=m;++i) {answ=max(answ,res1[i]+res2[m-i]);}
    cout<<answ;
    return 0;
}