#include <iostream>
#include <vector>
#include <algorithm>
#include <array>
#include <iterator>
#include <string>
#include <cctype>
#include <cstring>
#include <cstdlib>
#include <cassert>
#include <cmath>
#include <ctime>
#include <iomanip>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <bitset>
#include <random>
#include <utility>
#include <functional>
using namespace std;
void Main()
{
	int N;
	long long P;
	int K;
	cin >> N >> P >> K;
	const long long INF = (long long)1e18;
	vector<long long> dp(K + 1,-INF);
	dp[0] = P;
	for(int i = 0;i < N;i++)
	{
		int t,b;
		cin >> t >> b;
		if(t == 1)
		{
			for(int j = K;j >= 1;j--)
			{
				if(dp[j - 1] != -INF)
				{
					dp[j] = max(dp[j],dp[j - 1] + b);
					if(dp[j] > INF)
					{
						dp[j] = 2 * INF;
					}
				}
			}
		}
		else
		{
			for(int j = K;j >= 1;j--)
			{
				if(dp[j - 1] != -INF)
				{
					dp[j] = max(dp[j],dp[j - 1] * 2);
					if(dp[j] > INF)
					{
						dp[j] = 2 * INF;
					}
				}
			}
		}
	}
	long long ans = dp[K];
	if(ans == 2 * INF)
	{
		ans = -1;
	}
	cout << ans << "\n";
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int tt = 1;
	/* cin >> tt; */
	while(tt--) Main();
}