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

using ll = long long;
#define rep(i, n) for(int i = 0; i < n; i++)

int main() {
	int N, k;
	ll P;
	cin >> N >> P >> k;
	vector<int> t(N), b(N);
	rep(i, N) cin >> t[i] >> b[i];
	ll ans = 0, ma = 1e18;
	vector<vector<ll>> dp(N + 1, vector<ll>(k + 1));
	rep(i, N + 1) dp[i][0] = P;
	rep(i, N + 1) {
		rep(j, i) {
			if(j + 1 > k) break;
			int ii = i - 1;
			if(t[ii] == 1) dp[i][j + 1] = max(dp[i][j + 1], dp[i - 1][j] + b[ii]);
			else dp[i][j + 1] = max(dp[i][j + 1], dp[i - 1][j] * 2);
			if(dp[i][j + 1] > ma) {
				ans = -1;
				break;
			}
		}
		if(ans < 0) break;
	}
	if(ans < 0) {
		cout << -1 << endl;
		return 0;
	}
	rep(i, N + 1) {
		ans = max(ans, dp[i][k]);
	}
	cout << ans << endl;
}