#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <ctime>
#include <cassert>
#include <complex>
#include <string>
#include <cstring>
#include <chrono>
#include <random>
#include <bitset>
#include <fstream>
#include <array>
#include <functional>
#include <stack>
#include <memory>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcountll
#define ll long long
#define mp make_pair
#define x first
#define y second
#define Time (double)clock()/CLOCKS_PER_SEC
#define munq(a) sort(all(a)); a.resize(unique(all(a))-a.begin())
#define sz(a) ((int)a.size())

#ifdef LOCAL
#define debug(x) do { cout << #x << ": " << x << endl; } while(0)
#define debug2(x, y) do { std::cerr << #x << ", " << #y << ": " << x << ", " << y << endl; } while (0)
#define debug3(x, y, z) do {std::cerr << #x << ", " << #y << ", " << #z << ": " << x << ", " << y << ", " << z << endl; } while(0)
#else
#define debug(x)
#define debug2(x, y) 
#define debug3(x, y, z) 
#endif

#define FORI(i,a,b) for (int i = (a); i < (b); ++i)
#define FOR(i,a) FORI(i,0,a)
#define ROFI(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define ROF(i,a) ROFI(i,0,a)
#define rep(a) FOR(_,a)
#define each(a,x) for (auto& a: x)
#define FORN(i, n) FORI(i, 1, n + 1)

using vi = vector<int>;
template <typename T>
std::istream& operator >>(std::istream& input, std::pair <T, T> & data)
{
    input >> data.x >> data.y;
    return input;
}
template <typename T>
std::istream& operator >>(std::istream& input, std::vector<T>& data)
{
    for (T& x : data)
        input >> x;
    return input;
}
template <typename T>
std::ostream& operator <<(std::ostream& output, const pair <T, T> & data)
{
    output << "(" << data.x << "," << data.y << ")";
    return output;
}
template <typename T>
std::ostream& operator <<(std::ostream& output, const std::vector<T>& data)
{
    for (const T& x : data)
        output << x << " ";
    return output;
}
ll div_up(ll a, ll b) { return a/b+((a^b)>0&&a%b); } // divide a by b rounded up
ll div_down(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // divide a by b rounded down 
ll math_mod(ll a, ll b) { return a - b * div_down(a, b); }
#define tcT template<class T
#define tcTU tcT, class U
tcT> using V = vector<T>; 
tcT> bool ckmin(T& a, const T& b) {
    return b < a ? a = b, 1 : 0; 
} // set a = min(a,b)
tcT> bool ckmax(T& a, const T& b) {
    return a < b ? a = b, 1 : 0; 
}
tcT> vector <T> presum(vector <T> &a) {
    vector <T> p(a.size() + 1);
    FOR (i, a.size()) {
        p[i + 1] = p[i] + a[i];
    }   
    return p;
}
tcT> vector <T> sufsum(vector <T> &a) {
    vector <T> p(a.size() + 1);
    for (int i = (int)a.size() - 1; i >= 0; --i) {
        p[i] = p[i + 1] + a[i];
    }
    return p;
}
ll gcd(ll a, ll b) {
    while (b) {
        tie(a, b) = mp(b, a % b);
    }
    return a;
}
int Bit(int mask, int bit) { return (mask >> bit) & 1; }
struct Line {
    ll k, b;
 
    Line() : k(), b() {}
    Line (ll _k, ll _b) : k(_k), b(_b) {}
 
    ll getVal(ll x) {
        return b * x + k * (x * (x - 1) / 2);
    }
};
int intersect(Line a, Line b) {
    auto leftf = [&] (int l, int r, function <bool(int)> f) {
        //assert(!f(l)); assert(f(r));
        while (l < r - 1) {
            int m = (l + r) / 2;
            if (f(m)) {
                r = m;
            }
            else {
                l = m;
            }
        }
        return r;
    };
    auto f = [&] (int x) {
        return a.getVal(x)<=b.getVal(x);
    };
    return leftf(1, 1e9, f);
}
struct Hull {
    vector<Line> lines;
    vector<ll> borders;
 
    Hull() : lines(), borders() {}
 
    void addLine(Line L) {
        debug2(L.k,L.b);
        while(!lines.empty()) {
            debug(borders.back());
            debug(lines.back().getVal(borders.back()));
            debug(L.getVal(borders.back()));
            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(1LL); //leftmost query
            return;
        }
        if (lines.back().k == L.k) {
            return;
        }
        ll x = intersect(lines.back(),L);
        debug(x);
        lines.push_back(L);
        borders.push_back(x);
    }
    ll getMaxVal(ll x) {
        if (x == 0) {
            return 0;
        }
        int pos = upper_bound(borders.begin(), borders.end(), x) - borders.begin();
        if (pos == 0) throw;
        pos--;
        //debug(pos);
        //debug(lines[pos].k);
        return lines[pos].getVal(x);
    }
};
signed main() {
    #ifdef LOCAL
    #else
    #define endl '\n'
    ios_base::sync_with_stdio(0); cin.tie(0);
    #endif
    int n, m;
    cin >> n >> m;
    vi a(n), d(n);
    V <ii> l, g;
    priority_queue <ii> q;
    vi cur(n,1);
    FOR (i, n) {
        cin >> a[i] >> d[i];
        if (d[i]>=0) {
            l.app({d[i],a[i]});
        }
        else {
            int num = (int)g.size();
            q.push({a[i], num});
            g.app({d[i], a[i]});
        }
    }
    sort(all(l));
    Hull h;
    for (auto [k, b] : l) {
        h.addLine(Line(k,b));
    }

    int ans = -1e18, gre = 0;
    debug(g);
    FOR (i, m + 1) {
        //debug3(i,gre,h.getMaxVal(m - i));
        ckmax(ans, gre + h.getMaxVal(m - i));
        gre += q.top().x;
        //debug(q.top().x);
        int w = q.top().y; q.pop();
        cur[w]++;
        q.push({g[w].x*(cur[w]-1)+g[w].y,w});
    }
    cout << ans << endl;
}