#include <bits/stdc++.h>
#define int ll
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define rng(i,c,n) for(int i=c;i<n;i++)
#define fi first
#define se second
#define pb push_back
#define all(a) a.begin(), a.end()
#define sz(a) ((int) a.size())
#define vec(...) vector<__VA_ARGS__>
#define _4ab8goq ios::sync_with_stdio(0),cin.tie(0);
typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pii;
void print(){cout<<'\n';}
template<class h,class...t>
void print(const h&v,const t&...u){cout<<v<<' ',print(u...);}

void chmax(int&a,int b){
	a=max(a,b);
}

void chmin(int&a,int b){
	a=min(a,b);
}

void slv(){
	int n,p,k;
	cin>>n>>p>>k;

	vec(pii) a(n);
	rep(i,n){
		cin>>a[i].fi>>a[i].se;
	}

	const int inf=1e18;
	vi dp(k+1,-inf);
	dp[0]=p;
	rep(i,n){
		auto [t,b]=a[i];
		auto ndp=dp;
		rep(j,k){
			if(dp[j]==-inf) continue;
			if(t==1){
				chmax(ndp[j+1],min(inf,dp[j]+b));
			}else{
				chmax(ndp[j+1],min(inf,dp[j]*2));
			}
		}
		dp.swap(ndp);
	}
	if(dp[k]==inf) dp[k]=-1;
	cout<<dp[k]<<"\n";
}

signed main(){
_4ab8goq;
	slv();
}