#include <bits/stdc++.h>
using namespace std;
const long long INF = 1000000000000000001;
int main(){
  int N;
  long long P;
  int K;
  cin >> N >> P >> K;
  vector<int> T(N);
  vector<int> B(N);
  for (int i = 0; i < N; i++){
    cin >> T[i] >> B[i];
  }
  vector<vector<long long>> dp(N + 1, vector<long long>(N + 1, 0));
  dp[0][0] = P;
  for (int i = 0; i < N; i++){
    for (int j = 0; j <= i; j++){
      dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
      if (T[i] == 1){
        dp[i + 1][j + 1] = max(dp[i + 1][j], min(dp[i][j] + B[i], INF));
      }
      if (T[i] == 2){
        dp[i + 1][j + 1] = max(dp[i + 1][j], min(dp[i][j] * 2, INF));
      }
    }
  }
  if (dp[N][K] == INF){
    cout << -1 << endl;
  } else {
    cout << dp[N][K] << endl;
  }
}