#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i,a,b) for(it i=(it)(a);i<=(it)b;i++)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define moda 998244353LL
#define modb 1000000007LL
#define dai 2500000000000000000LL
#define tyu 2500000000
#define sho -dai
#define eps 1e-14
#define yn(x) cout<<(x ? "Yes":"No")<<endl;
#define YN(x) cout<<(x ? "YES":"NO")<<endl;
using it=long long;
using ll=long long;
using un=unsigned long long;
using db=long double;
using st=string;
using ch=char;
using bo=bool;
using P=pair<it,it>;
using T=tuple<it,it,it>;
using mint=modint;
using vi=vector<it>;
using vd=vector<db>;
using vs=vector<st>;
using vc=vector<ch>;
using vb=vector<bo>;
using vp=vector<P>;
using vm=vector<mint>;
using sp=set<P>;
using ss=set<st>;
using si=set<it>;
using vvi=vector<vi>;
using vvd=vector<vd>;
using vvs=vector<vs>;
using vvb=vector<vb>;
using vvc=vector<vc>;
using vvp=vector<vp>;
using vvm=vector<vm>;
using vsi=vector<si>;
using vsp=vector<sp>;
using vvsi=vector<vsi>;
using vvsp=vector<vsp>;
using vvvi=vector<vvi>;
using vvvd=vector<vvd>;
using vvvvi=vector<vvvi>;
const it dx[4]={0,1,0,-1};
const it dy[4]={1,0,-1,0};

int main(){
  it n,p,k;cin>>n>>p>>k;
  vi t(n),b(n);
  rep(i,0,n-1)cin>>t[i]>>b[i];
  vvi dp(n+1,vi(k+1,0));
  dp[0][0]=p;
  rep(i,0,n-1)
    rep(j,0,k){
      dp[i+1][j]=max(dp[i+1][j],dp[i][j]);
      if(j==k)break;
      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((db)(dp[i+1][j+1])>1e+18){
        cout<<-1<<endl;
        return 0;
      }
    }
  cout<<dp[n][k]<<endl;
}