#include <bits/stdc++.h>
using namespace std;
#define all(v) (v).begin(),(v).end()
#define pb(a) push_back(a)
#define rep(i, n) for(int i=0;i<n;i++)
#define foa(e, v) for(auto&& e : v)
using ll = long long;
const ll MOD7 = 1000000007, MOD998 = 998244353, INF = (1LL << 60);
#define dout(a) cout<<fixed<<setprecision(10)<<a<<endl;

void chmax(ll &a, ll b) { a = max(a, b); }
int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll inf = 1'000'000'000'000'000'000;
    ll n, P, k;
    cin >> n >> P >> k;
    vector<ll> dp(k + 1, -INF);
    dp[0] = P;
    rep(i, n) {
        ll t, b;
        cin >> t >> b;
        vector<ll> nx = dp;
        if(t == 2) {
            rep(j, k) {
                if(dp[j] * 2 > inf) {
                    cout << -1 << endl;
                    return 0;
                }
                chmax(nx[j + 1], dp[j] * 2);
            }
        } else {
            rep(j, k) {
                if(dp[j] + b > inf) {
                    cout << -1 << endl;
                    return 0;
                }
                chmax(nx[j + 1], dp[j] + b);
            }
        }
        swap(nx, dp);
    }
    cout << dp[k] << endl;
    return 0;
}