#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, k;
	long long p;
	cin >> n >> p >> k;
	vector dp(n + 1, vector<long long>(k + 2));
	dp[0][0] = p;
	rep(i, n) {
		int t, b; cin >> t >> b;
		if (1 == t) {
			rep(j, k + 1) {
				if (0 == dp[i][j])continue;
				chmax(dp[i + 1][j], dp[i][j]);
				if (dp[i][j] + b > LINF) dp[i + 1][j + 1] = LINF + 1;
				else chmax(dp[i + 1][j + 1], dp[i][j] + b);
			}
		}
		else {
			rep(j, k + 1) {
				if (0 == dp[i][j])continue;
				chmax(dp[i + 1][j], dp[i][j]);
				if (dp[i][j] * 2 > LINF) dp[i + 1][j + 1] = LINF + 1;
				else chmax(dp[i + 1][j + 1], dp[i][j] * 2);
			}
		}
	}
	long long ans = dp[n][k];
	if (ans > LINF)ans = -1;
	cout << ans << endl;
	return 0;
}