#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(v) v.begin(),v.end()
typedef long long ll;
 
#include<bits/stdc++.h>
using namespace std;

const ll INF=1000000000000000001;
ll dp[1010][1010];
 
int main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  
  ll n,p,k;
  cin>>n>>p>>k;
  vector<ll> T(n),B(n);
  rep(i,n) cin>>T[i]>>B[i];
  
  dp[0][k]=p;
  rep(i,n){
    rep(j,k+1){
      dp[i+1][j]=max(dp[i+1][j],dp[i][j]);
      if(dp[i][j]==INF) continue;
      if(j==0) continue;
      if(T[i]==1) dp[i+1][j-1]=max(dp[i+1][j-1],dp[i][j]+B[i]);
      else dp[i+1][j-1]=max(dp[i+1][j-1],dp[i][j]*2);
      if(dp[i+1][j-1]>=INF) dp[i+1][j-1]=INF;
    }
  }
  if(dp[n][0]==INF) cout<<-1<<endl;
  else cout<<dp[n][0]<<endl;
  
  return 0;
}