#ifdef NACHIA
#define _GLIBCXX_DEBUG
#else
#define NDEBUG
#endif
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <queue>
#include <array>
#include <cmath>
#include <atcoder/modint>
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(i64 i=0; i<(i64)(n); i++)
#define repr(i,n) for(i64 i=(i64)(n)-1; i>=0; i--)
const i64 INF = 1001001001001001001;
const char* yn(bool x){ return x ? "Yes" : "No"; }
template<typename A> void chmin(A& l, const A& r){ if(r < l) l = r; }
template<typename A> void chmax(A& l, const A& r){ if(l < r) l = r; }
template<typename A> using nega_queue = std::priority_queue<A,std::vector<A>,std::greater<A>>;
using Modint = atcoder::static_modint<998244353>;
//#include "nachia/vec.hpp"
using namespace std;

void testcase(){
    i64 N, P, K; cin >> N >> P >> K;
    vector<i64> dp;
    dp.push_back(P);
    rep(i,N){
        i64 t,b; cin >> t >> b;
        vector<i64> nx(dp.size()+1);
        rep(i,dp.size()) nx[i] = dp[i];
        if(t == 1){
            rep(i,dp.size()) chmax(nx[i+1], min(INF, dp[i] + b));
        } else {
            rep(i,dp.size()) chmax(nx[i+1], min(INF, dp[i] * 2));
        }
        swap(dp, nx);
    }
    i64 ans = dp[K];
    if(ans > 1'000'000'000'000'000'000) ans = -1;
    cout << ans << endl;
}

int main(){
    ios::sync_with_stdio(false); cin.tie(nullptr);
    #ifdef NACHIA
    int T; cin >> T; for(int t=0; t<T; T!=++t?(cout<<'\n'),0:0)
    #endif
    testcase();
    return 0;
}