#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

ll N,P,K;
ll dp[1010];

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>P>>K;
	FOR(i,K+1) dp[i]=-1LL<<60;
	dp[0]=P;
	FOR(i,N) {
		cin>>x>>y;
		for(j=K;j>=0;j--) {
			if(x==1) dp[j+1]=min(2LL<<60,max(dp[j+1],dp[j]+y));
			if(x==2) dp[j+1]=min(2LL<<60,max(dp[j+1],dp[j]*2));
		}
	}
	if(dp[K]>1000000000000000000LL) dp[K]=-1;
	cout<<dp[K]<<endl;
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}