#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int n, k;
  ll p;
  cin >> n >> p >> k;
  vector<pair<int, int>> v(n);
  rep(i, n) cin >> v[i].first >> v[i].second;
  constexpr ll INF = (ll) 1e18 + 1;
  vector dp(n + 1, vector<ll>(k + 1, -INF));
  dp[0][0] = p;
  rep(i, n) {
    rep(j, k + 1) {
      if (dp[i][j] == -INF) continue;
      dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
      if (j != k) {
        if (v[i].first == 1) {
          dp[i + 1][j + 1] = max(dp[i + 1][j + 1], min(dp[i][j] + v[i].second, INF));
        }
        else {
          dp[i + 1][j + 1] = max(dp[i + 1][j + 1], min(dp[i][j] * 2, INF));
        }
      }
    }
  }
  cout << (dp[n][k] == INF ? -1 : dp[n][k]) << endl;
  return 0;
}