#include<bits/stdc++.h>
using namespace std;
using ll=long long;
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
template<class T> bool chmax(T &a, T b){if (a < b){a = b;return true;} else return false;}
template<class T> bool chmin(T &a, T b){if (a > b){a = b;return true;} else return false;}

const ll INF=1'000'000'000'000'000'001;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N,K;
    ll P;
    cin>>N>>P>>K;
    vector<int>T(N);
    vector<ll>B(N);
    for(int i=0;i<N;i++)cin>>T[i]>>B[i];
    vector<ll>dp(K+1,-INF);
    dp[0]=P;
    for(int i=0;i<N;i++){
        vector<ll>dp2=dp;
        for(int j=0;j<K;j++){
            if(T[i]==1)chmax(dp2[j+1],dp[j]+B[i]);
            else chmax(dp2[j+1],2*dp[j]);
        }
        for(int j=0;j<=K;j++)chmin(dp2[j],INF);
        swap(dp,dp2);
    }
    if(dp[K]==INF)cout<<-1<<"\n";
    else cout<<dp[K]<<"\n";
}