#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using ll = long long;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using VD = vector<double>;
using VVD = vector<VD>;
using VS = vector<string>;
using P = pair<ll,ll>;
using VP = vector<P>;
#define rep(i, n) for (ll i = 0; i < ll(n); i++)
#define out(x) cout << x << endl
#define dout(x) cout << fixed << setprecision(10) << x << endl
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
#define sz(x) (int)(x.size())
#define re0 return 0
#define pcnt __builtin_popcountll
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
constexpr int inf = 1e9;
constexpr ll INF = 1e18;
//using mint = modint1000000007;
using mint = modint998244353;
int di[4] = {1,0,-1,0};
int dj[4] = {0,1,0,-1};

int main(){
    ll n,p,k;
    cin >> n >> p >> k;
    VL t(n),b(n);
    rep(i,n) cin >> t[i] >> b[i];
    VVL dp(n+1,VL(k+1,-INF));
    dp[0][0] = p;
    rep(i,n)rep(j,k+1){
        chmax(dp[i+1][j],dp[i][j]);
        chmin(dp[i+1][j],INF+1);
        if(j+1 <= k){
            if(t[i]==1) chmax(dp[i+1][j+1],dp[i][j]+b[i]);
            else chmax(dp[i+1][j+1],dp[i][j]*2);
            chmin(dp[i+1][j+1],INF+1);
        }
    }
    ll ans = dp[n][k];
    if(ans == INF+1){
        ans = -1;
    }
    out(ans);
}