#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define R cin>>
#define ln cout<<'\n'
#define ll long long
#define in(a) insert(a)
#define pb(a) push_back(a)
#define pd(a) printf("%.12f\n",a)
#define mem(a) memset(a,0,sizeof(a))
#define all(c) (c).begin(),(c).end()
#define iter(c) __typeof((c).begin())
#define rrep(i,n) for(ll i=(ll)(n)-1;i>=0;i--)
#define REP(i,m,n) for(ll i=(ll)(m);i<(ll)(n);i++)
#define rep(i,n) REP(i,0,n)
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
ll check(ll n,ll m,ll x,ll y){return x>=0&&x<n&&y>=0&&y<m;}void pr(){ln;}
template<class A,class...B>void pr(const A &a,const B&...b){cout<<a<<(sizeof...(b)?" ":"");pr(b...);}
template<class A>void PR(A a,ll n){rep(i,n)cout<<(i?" ":"")<<a[i];ln;}
const ll MAX=1e9+7,MAXL=1LL<<61,dx[8]={-1,0,1,0,-1,-1,1,1},dy[8]={0,1,0,-1,-1,1,1,-1};
typedef pair<ll,ll> P;

ll dp[1111][1111];

void Main() {
  ll n,p,k;
  cin >> n >> p >> k;
  P a[n];
  rep(i,n) cin >> a[i].F >> a[i].S;
  rep(i,n+1)rep(j,k+1) dp[i][j]=-MAXL;
  dp[0][0]=p;
  rep(i,n) {
    rep(j,k+1) {
      if(dp[i][j]<0) continue;
      dp[i+1][j]=max(dp[i+1][j],dp[i][j]);
      if(a[i].F==1) {
        dp[i+1][j+1]=max(dp[i+1][j+1],dp[i][j]+a[i].S);
      } else {
        dp[i+1][j+1]=max(dp[i+1][j+1],dp[i][j]*2);
      }
      if(dp[i+1][j+1]<dp[i][j]||dp[i+1][j+1]>1000000000000000000LL) {
        pr(-1);
        return;
      }
    }
  }
  pr(dp[n][k]);
}

int main(){ios::sync_with_stdio(0);cin.tie(0);Main();return 0;}