#include <iostream>
#include <sstream>
#include <string>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cassert>
#include <numeric>

using namespace std;

#define FOR(i,k,n) for(int i=(k); i<(int)n; ++i)
#define REP(i,n) FOR(i,0,n)
#define FORIT(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)

template<class T> void debug(T begin, T end){ for(T i = begin; i != end; ++i) cout<<*i<<" "; cout<<endl; }

typedef long long ll;
const int INF = 100000000;
const double EPS = 1e-8;
const int MOD = 1000000007;
typedef pair<double, double> P;
bool compare(P p, P q){
  if((double)p.second * q.first != (double)q.second * p.first) return (double)p.second * q.first > (double)q.second * p.first; //rev
  else return p.first < q.first;
}
bool compare2(P p, P q){
  return !compare(p, q);
  if((double)p.second/p.first != (double)q.second/q.first) return (double)p.second/p.first < (double)q.second/q.first; //rev
  else return p.first < q.first;
}

int main(){
  int N;
  ll W;
  while(cin>>N>>W && N){
    vector<int> w(N), v(N);
    REP(i, N) cin>>w[i]>>v[i];
    vector<bool> used(N, 0);
    vector<P> get;
    vector<P> reduce;
    double ans = 0;
    REP(i, N){
      if(w[i] == 0){
        if(v[i] >= 0) ans += v[i];
        used[i] = true;
      }else if(w[i] < 0 && v[i] >= 0){
        ans += v[i];
        W -= w[i];
        used[i] = true;
      }else if(w[i] > 0 && v[i] <= 0){
        used[i] = true;
      }
    }
    REP(i, N)if(!used[i]){
      if(w[i] > 0){ assert(v[i] > 0); get.push_back(P(w[i], v[i])); }
      else { assert(v[i] < 0); reduce.push_back(P(w[i], v[i])); }
    }
    sort(get.begin(), get.end(), compare);
    sort(reduce.begin(), reduce.end(), compare2);
    int r_idx = 0;
    REP(i, get.size()){
      if(get[i].first <= W){
        W -= get[i].first;
        ans += get[i].second;
      }else{
        while(r_idx < reduce.size() && get[i].first > W && get[i].first/get[i].second < reduce[r_idx].first/reduce[r_idx].second){
          if(W - reduce[r_idx].first < get[i].first){
            W -= reduce[r_idx].first;
            ans += reduce[r_idx].second;
            r_idx++;
          }else{
            double rest = get[i].first - W;
            assert(rest > 0);
            double use_p = rest/abs(reduce[r_idx].first);
            assert(abs(W - reduce[r_idx].first * use_p - get[i].first) < 0.001);
            W = get[i].first;
            ans += reduce[r_idx].second * use_p;
            reduce[r_idx].first += rest;
            reduce[r_idx].second = (reduce[r_idx].second - reduce[r_idx].second * use_p);
          }
        }
        if(get[i].first <= W){
          W -= get[i].first;
          ans += get[i].second;
        }else if(W > 0){
          double p = (double)W/get[i].first;
          assert(0 < p && p < 1);
          W = 0;
          ans += get[i].second * p;
        }
      }
    }
    printf("%.6lf\n", ans);
  }
  return 0;
}