#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, n) for(int i = a; i < n; i++)
#define rrep(i, a, n) for(int i = a; i >= n; i--)
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
// constexpr ll MOD = 1000000007;
constexpr ll MOD = 998244353;
constexpr int IINF = 1001001001;
constexpr ll INF = 1LL<<60;

template<class t,class u> void chmax(t&a,u b){if(a<b)a=b;}
template<class t,class u> void chmin(t&a,u b){if(b<a)a=b;}

int main(){
    ll n, p, k; cin >> n >> p >> k;
    vector<vector<ll>> dp(n+1, vector<ll>(k+1, -1));
    ll m = 1e18;
    dp[0][0] = p;
    rep(i, 1, n+1){
        int t;
        ll b; cin >> t >> b;
        if(t == 1){
            rep(j, 0, k+1){
                if(dp[i-1][j] >= 0) chmax(dp[i][j], dp[i-1][j]);
                if(j > 0 && dp[i-1][j-1] >= 0) chmax(dp[i][j], dp[i-1][j-1]+b);
                if(dp[i][j] > m){
                    cout << -1 << endl;
                    return 0;
                }
            }
        }else{
            rep(j, 0, k+1){
                if(dp[i-1][j] >= 0) chmax(dp[i][j], dp[i-1][j]);
                if(j > 0 && dp[i-1][j-1] >= 0) chmax(dp[i][j], 2*dp[i-1][j-1]);
                if(dp[i][j] > m){
                    cout << -1 << endl;
                    return 0;
                }
            }
        }
    }

    cout << dp[n][k] << endl;
    return 0;
}