#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2")
#include <bits/stdc++.h>
#define INF 1000000001LL
#define LNF 1000000000000000001LL
#define MOD 998244353LL
#define MAX 2001
#define long long long
#define all(x) x.begin(),x.end()
using namespace std;

int main()
{
	ios_base::sync_with_stdio(0); 
    cin.tie(0);

    long n,p,k;
    cin >> n >> p >> k;

    long dp[n+1][k+1];

    memset(dp,0,sizeof dp);

    dp[0][0] = p;

    for(int i = 1; i<=n; i++)
    {
        long a,b;
        cin >> a >> b;

        dp[i][0] = p;
        for(int j = 0; j<k; j++)
        {
            if(a == 1)
            {
                dp[i][j+1] = max(dp[i-1][j+1],dp[i-1][j]+b);
            }
            else
                dp[i][j+1] = max(dp[i-1][j+1],dp[i-1][j]*2);
            if(dp[i][j+1] > LNF)
                dp[i][j+1] = LNF;
        }
    }

    if(dp[n][k] == LNF)
        cout << -1 << endl;
    else
        cout << dp[n][k] << endl;

    return 0;
}