// wrong answer
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <queue>
#include <atcoder/modint>
using namespace std;
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(i64 i=0; i<(i64)(n); i++)
#define repr(i,n) for(i64 i=(i64)(n)-1; i>=0; i--)
const i64 INF = 1001001001001001001;
using Modint = atcoder::static_modint<998244353>;


int main(){
    ios::sync_with_stdio(false); cin.tie(nullptr);
    i64 N, M; cin >> N >> M;
    vector<pair<i64, i64>> A, B;
    rep(i,N){
        i64 a,d; cin >> a >> d;
        if(d <= 0) B.push_back({ d, a });
        else A.push_back({ d, a });
    }
    auto nthTerm = [](i64 d, i64 a, i64 n) -> i64 {
        return a + d * n;
    };
    auto prefixSum = [](i64 d, i64 a, i64 n) -> i64 {
        i64 ans = a * n;
        ans += d * ((n*n-n)/2);
        return ans;
    };
    vector<i64> valdown;
    {
        int n = B.size();
        vector<int> ptr(n);
        priority_queue<pair<i64, i64>> que;
        rep(v,n){
            auto [d,a] = B[v];
            que.push({ nthTerm(d, a, ptr[v]), v });
        }
        rep(i,M){
            auto [p,v] = que.top(); que.pop();
            valdown.push_back(p);
            ptr[v]++;
            auto [d,a] = B[v];
            que.push({ nthTerm(d, a, ptr[v]), v });
        }
    }
    vector<i64> valdownSum(M+1);
    rep(i,M) valdownSum[i+1] = valdownSum[i] + valdown[i];
    i64 ans = valdownSum[M];
    for(auto [d,a] : A){
        i64 ok = 0, ng = M+1;
        while(ok + 1 < ng){
            i64 x = (ok + ng) / 2;
            if(nthTerm(d,a,x-1) >= valdown[M-x]) ok = x; else ng = x;
        }
        ans = max(ans, valdownSum[M-ok] + prefixSum(d,a,ok));
    }
    cout << ans << endl;
    return 0;
}