#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 1000000000000000001

int main(){
	
	ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	
	long long N,P,K;
	cin>>N>>P>>K;
	vector<long long> dp(K+1,0);
	dp[0] = P;
	rep(i,N){
		int t;
		long long B;
		cin>>t>>B;
		vector<long long> ndp(K+1,0);
		rep(j,K+1){
			ndp[j] = max(ndp[j],dp[j]);
			if(j+1<=K){
				if(t==1)ndp[j+1] = max(ndp[j+1],dp[j] + B);
				else ndp[j+1] = max(ndp[j+1],dp[j] *2);
			}
		}
		rep(j,K+1)ndp[j] = min(ndp[j],(long long)Inf64);
		swap(dp,ndp);
		
	}
	long long ans = dp.back();
	if(ans==Inf64)ans = -1;
	cout<<ans<<endl;
	return 0;
}