#include <bits/stdc++.h>
using namespace std;

long long INF = 1000000000000000001;

int main() {
    int n, k;
    long long p;
    cin >> n >> p >> k;
    vector<int> t(n);
    vector<long long> b(n);
    for (int i = 0; i < n; i++) {
        cin >> t[i] >> b[i];
    }
    //dp[i][j] := i番目まで見て、装備をk個使った状態
    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 <= k; j++) {
            dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
            if (j == k) {
                continue;
            }
            if (dp[i][j] == 0LL) {
                continue;
            }
            if (t[i] == 1) {
                long long x = min(INF, dp[i][j] + b[i]);
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], x);
            } else {
                long long x = min(INF, dp[i][j] * 2LL);
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], x);
            }
        }
    }
    cout << (dp[n][k] == INF ? -1 : dp[n][k]) << endl;
}