#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef unsigned long long int ull;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myRand(ll B) {
    return (ull)rng() % B;
}
inline double time() {
    return static_cast<long double>(chrono::duration_cast<chrono::nanoseconds>(chrono::steady_clock::now().time_since_epoch()).count()) * 1e-9;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n; cin >> n;
    ll P; cin >> P;
    int k; cin >> k;
    const ll inf = 1e18;
    vector<ll> dp(k+1, -1);
    dp[0] = P;
    for (int i = 0; i < n; ++i) {
        int t; cin >> t;
        ll b; cin >> b;
        for (int j = k-1; j >= 0; --j) {
            if (dp[j] == -1) continue;
            ll nxt = dp[j];
            if (t == 1) nxt += b;
            else nxt *= 2;
            if (nxt > inf) {
                cout << -1 << endl;
                return 0;
            }
            dp[j+1] = max(dp[j+1], nxt);
        }
    }
    cout << dp[k] << endl;
}