#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<vector<int>> vvi;
typedef vector<vector<long long>> vvl;
typedef long double ld;
typedef pair<int, int> P;

ostream& operator<<(ostream& os, const modint& a) {os << a.val(); return os;}
template <int m> ostream& operator<<(ostream& os, const static_modint<m>& a) {os << a.val(); return os;}
template <int m> ostream& operator<<(ostream& os, const dynamic_modint<m>& a) {os << a.val(); return os;}
template<typename T> istream& operator>>(istream& is, vector<T>& v){int n = v.size(); assert(n > 0); rep(i, n) is >> v[i]; return is;}
template<typename U, typename T> ostream& operator<<(ostream& os, const pair<U, T>& p){os << p.first << ' ' << p.second; return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : " "); return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<vector<T>>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : ""); return os;}

template<typename T> void chmin(T& a, T b){a = min(a, b);}
template<typename T> void chmax(T& a, T b){a = max(a, b);}

const long long INF = 1000000000000000001;

int main(){
	int n, k;
	long long p;
	cin >> n >> p >> k;
	vector<long long> dp(k + 1, -1);
	dp[0] = p;
	rep(i, n){
		vector<long long> dp_old(k + 1, -1);
		swap(dp, dp_old);
		int t;
		long long b;
		cin >> t >> b;
		rep(from, k + 1){
			if(dp_old[from] == -1) continue;
			chmax(dp[from], dp_old[from]);
			if(from < k){
				long long val = dp_old[from];
				if(t == 1){
					val += b;
					chmax(dp[from + 1], min(val, INF));
				}
				if(t == 2){
					val *= 2;
					chmax(dp[from + 1], min(val, INF));
				}
			}
		}
//		cout << dp;
	}
	if(dp[k] >= INF) cout << "-1\n";
	else cout << dp[k] << "\n";
	return 0;
}