#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;

void IO(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
}

int main(){
  IO();
  ll n,p,k;
  cin>>n>>p>>k;
  vector<ll> t(n),b(n);
  for(ll i=0;i<n;i++){
    cin>>t[i]>>b[i];
  }
  vector<vector<ll>> dp(n+1,vector<ll>(k+1,-1e18));
  dp[0][0]=p;
  for(ll i=0;i<n;i++){
    for(ll j=0;j<=k;j++){
      if(t[i]==1){
        if(dp[i][j]==-1e18){
          continue;
        }
        if(j+1<=k){
          ll kouho=dp[i][j]+b[i];
          if(kouho>1e18){
            cout<<-1<<endl;
            exit(0);
          }
          dp[i+1][j+1]=max(dp[i+1][j+1],dp[i][j]+b[i]);
        }
        dp[i+1][j]=max(dp[i+1][j],dp[i][j]);
      }else{
        if(dp[i][j]==-1e18){
          continue;
        }
        if(j+1<=k){
          ll kouho=2*dp[i][j];
          if(kouho>1e18){
            cout<<-1<<endl;
            exit(0);
          }
          dp[i+1][j+1]=max(dp[i+1][j+1],2*dp[i][j]);
        }
        dp[i+1][j]=max(dp[i+1][j],dp[i][j]);
      }
    }
  }
  cout<<dp[n][k]<<endl;
}