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

long long MAX = 1e18;
int main()
{
    int N, K;
    long long P;
    cin >> N >> P >> K;
    vector<int> T(N);
    vector<int> B(N);
    for (int i = 0; i < N; i++)
    {
        cin >> T[i] >> B[i];
    }
    vector<long long> dp(N + 1, -1);
    dp[0] = P;
    for (int i = 0; i < N; i++)
    {
        for (int j = i; j >= 0; j--)
        {
            if (dp[j] == -1)
            {
                continue;
            }
            long long val = 0;
            if (T[i] == 1)
            {
                if (dp[j] + B[i] > MAX)
                {
                    val = MAX + 1;
                }
                else
                {
                    val = dp[j] + B[i];
                }
            }
            if (T[i] == 2)
            {

                if (dp[j] > MAX / 2)
                {
                    val = MAX + 1;
                }
                else
                {
                    val = dp[j] * 2;
                }
            }
            dp[j + 1] = max(dp[j + 1], val);
        }
    }
    if (dp[K] > MAX)
    {
        cout << -1;
    }
    else
    {
        cout << dp[K];
    }
}