#include<bits/stdc++.h>
// #include<atcoder/all>
// #include<boost/multiprecision/cpp_int.hpp>

using namespace std;
// using namespace atcoder;
// using bint = boost::multiprecision::cpp_int;
using ll = long long;
using ull = unsigned long long;
using P = pair<int,int>;
using vi = vector<ll>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
#define rep(i,n) for(ll i = 0;i < (ll)n;i++)
#define ALL(x) (x).begin(),(x).end()
#define sz(c) ((ll)(c).size())
#define LB(A,x) (int)(lower_bound(A.begin(),A.end(),x)-A.begin())
// #define MOD 1000000007
#define MOD 998244353
template<typename T>using min_priority_queue=priority_queue<T,vector<T>,greater<T>>;
template<typename T>ostream&operator<<(ostream&os,vector<T>&v){for(int i = 0;i < v.size();i++)os<<v[i]<<(i+1!=v.size()?" ":"");return os;}
template<typename T>istream&operator>>(istream&is,vector<T>&v){for(T&in:v)is>>in;return is;}
template<typename T1,typename T2>ostream&operator<<(ostream&os,pair<T1,T2>&p){os<<p.first<<" "<<p.second;return os;}
template<typename T1,typename T2>istream&operator>>(istream&is,pair<T1,T2>&p){is>>p.first>>p.second;return is;}



int main(){
  
  ios_base::sync_with_stdio(0), cin.tie(0);
  ll n,p,K;
  cin >> n >> p >> K;
  vi dp(K+1,-2);
  dp[0] = p;
  rep(i,n){
    ll t,b;cin >> t >> b;
    vi DP(K+1,-2);
    rep(j,K+1){
      if(dp[j] == -2)continue;
      if(dp[j] == -1){
        DP[j] = -1;
        if(j != K)DP[j+1] = -1;
      }else{
        if(DP[j] != -1)DP[j] = max(DP[j],dp[j]);
        if(j != K && DP[j+1] != -1){
          if(t == 1)DP[j+1] = max(DP[j+1],dp[j] + b);
          else DP[j+1] = max(DP[j+1],2*dp[j]);
          if(DP[j+1] > 1e18)DP[j+1] = -1;
        }
      }
    }
    swap(dp,DP);
  }
  cout << dp[K] << "\n";
  

  return 0;
}