#include<bits/stdc++.h>
#include<atcoder/all>

using namespace std;

using int64 = long long;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;

template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 >& p) {
  os << p.first << " " << p.second;
  return os;
}

template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename F >
struct FixPoint : F {
  explicit FixPoint(F &&f) : F(forward< F >(f)) {}

  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};

template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint<F>{forward<F>(f)};
}


int main() {
  int N, K;
  int64 P;
  cin >> N >> P >> K;
  auto dp = make_v< __int128_t >(K + 1, 64);
  fill_v(dp, -1);
  dp[0][0] = P;
  for(int i = 0; i < N; i++) {
    int t, b;
    cin >> t >> b;
    if(t == 1) {
      for(int j = K - 1; j >= 0; j--) {
        for(int k = 62; k >= 0; k--) {
          if(~dp[j][k]) {
            chmax(dp[j + 1][k], dp[j][k] + b);
          }
        }
      }
    } else {
      for(int j = K - 1; j >= 0; j--) {
        for(int k = 61; k >= 0; k--) {
          if(~dp[j][k]) {
            chmax(dp[j + 1][k + 1], dp[j][k] * 2);
          }
        }
      }
    }
    for(int j = 0; j <= K; j++) {
      for(int k = 0; k < 64; k++) {
        if(dp[j][k] >= (int64)1e18) {
          cout << -1 << endl;
          return 0;
        }
      }
    }
  }
  int64 ret = 0;
  for(auto& p : dp[K]) chmax(ret, p);
  cout << ret << endl;
}