#include <bits/stdc++.h>

using namespace std;
void fast_io() {
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
}

int main() {
    fast_io();
    const long long INF = (long long)1e18 + 1;
    int n, k;
    long long p;
    cin >> n >> p >> k;
    vector<long long> t(n), b(n);
    for (int i = 0; i < n; i++) {
        cin >> t[i] >> b[i];
    }
    vector<vector<long long>> dp(n + 1, vector<long long>(k + 1));
    dp[0][0] = p;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= min(i, k); j++) {
            dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
            if (j < k) {
                long long p_new = dp[i][j];
                if (t[i] == 1) {
                    p_new += b[i];
                } else {
                    p_new *= 2;
                }
                p_new = min(p_new, INF);
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], p_new);
            }
        }
    }
    if (dp[n][k] == INF) {
        cout << -1 << endl;
    } else {
        cout << dp[n][k] << endl;
    }
}