#include<bits/stdc++.h>
using namespace std;
using ll=long long;
ll INF=1000000000000000000;
int main(){
  ll n,p,k,t,b,x;cin>>n>>p>>k;vector<ll> A(k+1,-1);A[0]=p;
  for(int i=1;i<=n;i++){
    cin>>t>>b;
    for(int j=k-1;j>=0;j--){
      if(A[j]>=1){
        x=A[j];
        if(t==1)x=min(x+b,INF+1);
        if(t==2)x=min(x*2,INF+1);
        A[j+1]=max(A[j+1],x);
      }
    }
  }
  cout<<(A[k]==INF+1?-1:A[k]);
}