#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <fstream>
#include <sstream>
#include<set>
#include<stack>
#include<time.h>
#include <sys/types.h>
#include <tuple>
#include <numeric>
#include <iterator>

typedef long long int ll;
//#include<bits/stdc++.h>


using namespace std;

ll gcd(ll a, ll b) {
    if (a < b)swap(a, b);
    if (b == 0)return a;
    return gcd(b, a % b);
}
int lcm(int a, int b) {
    return a * b / gcd(a, b);
}




int main()
{

    int Q;
    Q = 1;
    //cin >> Q;   

    while (Q--) {
        int n;
        cin >> n;
        ll p, k;
        cin >> p >> k;
        int b = 0; vector<vector<ll>>a(n+5,vector<ll>(n+5));
        a[0][0]=p;
        for (int i = 0; i < n; i++) {
            a[i + 1] = a[i];
            int x, y;
            cin >> x >> y;
            if (x == 2) {
                for (int j = 0; j <= i; j++) {
                    a[i + 1][j + 1] = max(a[i + 1][j + 1], a[i][j] * 2);
                    if (a[i + 1][j + 1] >= 1e18 && j <= k) {
                        cout << -1; return 0;
                    }
                }
            }
            else {
                for (int j = 0; j <=i; j++) {
                    a[i + 1][j + 1] = max(a[i + 1][j + 1], a[i][j] +y);
                    if (a[i + 1][j + 1] >= 1e18 && j <= k) {
                        cout << -1; return 0;
                    }
                }
            }
            
        }
        
        ll ans = p;
        for (int i = 0; i <= n; i++) {
            ans = max(ans, a[i][k]);
            
        }
        cout << ans;
    }
        return 0;
}