#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

ll N, P, K, T[1010], B[1010];
ll dp[1010][1010];

int main() {
  cin >> N >> P >> K;
  for (int i = 0; i < N; i++) {
    cin >> T[i] >> B[i];
  }
  dp[0][0] = P;
  for (int i = 0; i < N; i++) {
    for (int j = 0; j <= min(i, (int)K); j++) {
      dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
      if (j < K) {
        if (T[i] == 1) dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j] + B[i]);
        if (T[i] == 2) dp[i + 1][j + 1] = max(dp[i + 1][j + 1], 2LL * dp[i][j]);
        dp[i + 1][j + 1] = min(dp[i + 1][j + 1], 1'000'000'000'000'000'001LL);
      }
    }
  }
  if (dp[N][K] > 1'000'000'000'000'000'000LL) cout << -1 << endl;
  else cout << dp[N][K] << endl;
  return 0;
}