// #pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
// #include <x86intrin.h>
using namespace std;
#if __cplusplus >= 202002L
using namespace numbers;
#endif
template<class T> T &ctmin(T &x){ return x; }
template<class T, class Head, class ...Tail> T &ctmin(T &x, const Head &h, const Tail &... t){ return ctmin(x = min<T>(x, h), t...); }
template<class T> T &ctmax(T &x){ return x; }
template<class T, class Head, class ...Tail> T &ctmax(T &x, const Head &h, const Tail &... t){ return ctmax(x = max<T>(x, h), t...); }



int main(){
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(ios::badbit | ios::failbit);
	int n, k;
	long long init;
	cin >> n >> init >> k;
	const long long minf = -4e18, th = 1e18;
	vector<long long> dp(k + 1, minf);
	dp[0] = init;
	for(auto i = 0; i < n; ++ i){
		int type, delta;
		cin >> type >> delta;
		if(type == 1){
			for(auto x = k; x >= 1; -- x){
				ctmax(dp[x], min(th + 1, dp[x - 1] + delta));
			}
		}
		else{
			for(auto x = k; x >= 1; -- x){
				ctmax(dp[x], min(th + 1, 2 * dp[x - 1]));
			}
		}
	}
	dp[k] > th ? cout << "-1\n" : cout << dp[k] << "\n";
	return 0;
}

/*

*/