#include<bits/stdc++.h>
using namespace std;
#include<atcoder/all>
using namespace atcoder;
#define rep(i,n) for (int i = 0; i < (n); ++i)
using ld = long double;
using ll = long long;

template<class T> bool chmax(T &a, T b)
{
	if(a<b)
	{
	a = b;
	return true;
	}
	return false;
}
template<class T> bool chmin(T &a, T b)
{
	if(a>b)
	{
		a = b;
		return true;
	}
	return false;
}

int N, K, T[1<<10], B[1<<10];
ll P, dp[1<<10][1<<10];
const ll inf = 1e18;

int main()
{
	cin >> N >> P >> K;
	rep(i,N) cin >> T[i] >> B[i];

	dp[0][0] = P;
	rep(i,N) rep(j,K+1)
	{
		if(dp[i][j]>inf)
		{
			cout << -1 << endl;
			return 0;
		}
		chmax(dp[i+1][j], dp[i][j]);
		if(j<K&&T[i]==1) chmax(dp[i+1][j+1], dp[i][j]+B[i]);
		if(j<K&&T[i]==2) chmax(dp[i+1][j+1], dp[i][j]*2);
	}
	ll ans = 0;
	rep(i,N+1) chmax(ans, dp[i][K]);
	cout << (ans<=inf?ans:-1) << endl;
}