#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 A(n+1,vector<ll>(k+1,-1));A[0][0]=p;
  for(int i=1;i<=n;i++){
    cin>>t>>b;A[i]=A[i-1];
    for(int j=0;j<k;j++){
      if(A[i-1][j]>=0&&A[i-1][j]<=INF){
        x=A[i-1][j];
        if(t==1)A[i][j+1]=max(min(x+b,INF+1),A[i][j+1]);
        if(t==2)A[i][j+1]=max(min(x*2,INF+1),A[i][j+1]);
      }
    }
  }
  cout<<(A[n][k]==INF+1?-1:A[n][k]);
}