#include <bits/stdc++.h>

using namespace std;

using i64 = long long;

#define yn(pope) (pope ? "Yes" : "No")

#define rep(i, n, m) for (int i = (n); i < (m); i++)
#define rrep(i, n, m) for (int i = (n); i > m; i--)

#define IINF (1 << 30)
#define INF (1ll << 60)

#define all(v) v.begin(), v.end()

int main() {
  int N, K;
  i64 P;
  cin >> N >> P >> K;

  vector dp(K + 1, 0ll);

  dp[0] = P;

  rep(_, 0, N) {
    int t;
    i64 b;
    cin >> t >> b;

    vector cp = dp;

    if (t == 1) {
      rep(i, 0, K) { cp[i + 1] = max(dp[i + 1], dp[i] + b); }
    }

    if (t == 2) {
      rep(i, 0, K) { cp[i + 1] = max(dp[i + 1], dp[i] << 1); }
    }

    dp = cp;

    rep(i, 0, K + 1) {
      if (dp[i] >= 1000000000000000000ll) {
        dp[i] = 1000000000000000000ll;
      }
    }
  }

  cout << (dp[K] > 1000000000000000000ll ? -1 : dp[K]) << endl;

  return 0;
}