#include<bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;

#define all(v) v.begin(),v.end()
using ll = long long;
using ull = unsigned long long;
using lll = __int128;
using vll=vector<ll>;
using vvll = vector<vector<ll>>;
using P = pair<ll,ll>;
using vp=vector<pair<ll, ll>>;
//using mint=modint1000000007;
//using mint=modint998244353;

const ll INF=1ll<<60;
ll mod10=1e9+7;
ll mod99=998244353;
const double PI = acos(-1);

#define rep(i,n) for (ll i=0;i<n;++i)
#define per(i,n) for(ll i=n-1;i>=0;--i)
#define rep2(i,a,n) for (ll i=a;i<n;++i)
#define per2(i,a,n) for (ll i=a;i>=n;--i)

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return true; } return false; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return true; } return false; }

bool solve(){
    ll N,M;cin>>N>>M;
    vll C(N),D(N);rep(i,N) cin>>C[i]>>D[i];
    vll ind(N);rep(i,N) ind[i]=i;
    auto comp = [&](ll i,ll j){
        return C[i]>C[j];
    };
    sort(all(ind),comp);
    vvll dp(M+2,vll(16,(ll)-INF));
    dp[0][0]=0;
    rep(i2,N){
        vvll dp2(M+2,vll(16,-INF));
        rep(j,M+1) rep(k,14){
            ll i=ind[i2];
            ll c=C[i]*(1ll<<k);
            //cout << i2<<" "<<i<<" "<<j<<" "<<k<<" "<<dp[i][j][k] <<" "<<c<<" "<<D[i]<< endl;
            
            chmax(dp2[min(M+1,j+c)][k+1],dp[j][k]+D[i]);
            chmax(dp2[j][k],dp[j][k]);
            if(c==0) chmax(dp2[j][k],dp[j][k]+D[i]);
        }
        swap(dp,dp2);
    }
    
    ll ans=0;
    rep(j,M+1) rep(k,16) chmax(ans,dp[j][k]);
    cout << ans << endl;
    return 0;
}



int main(){
   cin.tie(0);
   ios::sync_with_stdio(false);
   ll T=1;//cin>>T;
   rep(i,T) solve();
}