#include <bits/stdc++.h>
using namespace std;
#define overload1(a, ...) a
#define overload2(a, b, ...) b
#define overload3(a, b, c, ...) c
#define overload4(a, b, c, d, ...) d
#define overload5(a, b, c, d, e ...) e
#define overload6(a, b, c, d, e, f ...) f
#define overload7(a, b, c, d, e, f, g ...) g
#define fast_io ios::sync_with_stdio(false); cin.tie(nullptr);
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")
typedef long long ll;
typedef long double ld;
#define chmin(a,b) a = min(a,b);
#define chmax(a,b) a = max(a,b);
#define bit_count(x) __builtin_popcountll(x)
#define leading_zero_count(x) __builtin_clz(x)
#define trailing_zero_count(x) __builtin_ctz(x)
#define gcd(a,b) __gcd(a,b)
#define lcm(a,b) a / gcd(a,b) * b
#define rep(...) overload4(__VA_ARGS__, rrep, rep1, rep0)(__VA_ARGS__)
#define rep0(n) for(int _ = 0 ; _ < n ; _++)
#define rep1(i,n) for(int i = 0 ; i < n ; i++)
#define rrep(i,a,b) for(int i = a ; i < b ; i++)
#define repi(it,S) for(auto it = S.begin() ; it != S.end() ; it++)
#define pt(a) cout << a << endl;
#define print(...) printall(__VA_ARGS__);
#define debug(a) cout << #a << " " << a << endl;
#define all(a) a.begin(), a.end()
#define endl "\n";
#define v1(T,n,a) vector<T>(n,a)
#define v2(T,n,m,a) vector<vector<T>>(n,v1(T,m,a))
#define v3(T,n,m,k,a) vector<vector<vector<T>>>(n,v2(T,m,k,a))
#define v4(T,n,m,k,l,a) vector<vector<vector<vector<T>>>>(n,v3(T,m,k,l,a))
template<typename T,typename U>istream &operator>>(istream&is,pair<T,U>&p){is>>p.first>>p.second;return is;}
template<typename T,typename U>ostream &operator<<(ostream&os,const pair<T,U>&p){os<<p.first<<" "<<p.second;return os;}
template<typename T>istream &operator>>(istream&is,vector<T>&v){for(T &in:v){is>>in;}return is;}
template<typename T>ostream &operator<<(ostream&os,const vector<T>&v){for(auto it=v.begin();it!=v.end();){os<<*it<<((++it)!=v.end()?" ":"");}return os;}
template<typename T>istream &operator>>(istream&is,vector<vector<T>>&v){for(T &in:v){is>>in;}return is;}
template<typename T>ostream &operator<<(ostream&os,const vector<vector<T>>&v){for(auto it=v.begin();it!=v.end();){os<<*it<<((++it)!=v.end()?"\n":"");}return os;}
template<typename T>ostream &operator<<(ostream&os,const set<T>&v){for(auto it=v.begin();it!=v.end();){os<<*it<<((++it)!=v.end()?" ":"");}return os;}
template<typename T>ostream &operator<<(ostream&os,const multiset<T>&v){for(auto it=v.begin();it!=v.end();){os<<*it<<((++it)!=v.end()?" ":"");}return os;}
template<class... Args> void printall(Args... args){for(auto i:initializer_list<common_type_t<Args...>>{args...}) cout<<i<<" ";cout<<endl;}

struct Int128t {
    __int128_t x;

    Int128t() {}
    Int128t(const long long &a) { x = a; }
    Int128t(const string &s) { parse(s); }

    long long long_val() { return (long long)x; }
    __int128_t val() { return x; }
    __int128_t abs() { return x < 0 ? -x : x; }

    void set(const long long &a) { x = a; }

    void parse(const string &s) {
        x = 0;
        for ( char c : s ) {
        if ( isdigit(c) ) x = x * 10 + (c - '0');
        }
        if ( s[0] == '-' ) x *= -1;
    }

    Int128t operator+=(const Int128t &a) {
        x += a.x;
        return *this;
    }
    Int128t operator-=(const Int128t &a) {
        x -= a.x;
        return *this;
    }
    Int128t operator*=(const Int128t &a) {
        x *= a.x;
        return *this;
    }
    Int128t operator/=(const Int128t &a) {
        x /= a.x;
        return *this;
    }
    Int128t operator%=(const Int128t &a) {
        x %= a.x;
        return *this;
    }

    Int128t& operator++() {
        ++x;
        return *this;
    }

    Int128t operator++(int) {
        Int128t tmp(*this);
        ++x;
        return tmp;
    }

    Int128t& operator--() {
        --x;
        return *this;
    }

    Int128t operator--(int) {
        Int128t tmp(*this);
        --x;
        return tmp;
    }

    Int128t operator-() const { return Int128t(-x); }

    Int128t operator+(const Int128t &p) const { return Int128t(*this) += p; }

    Int128t operator-(const Int128t &p) const { return Int128t(*this) -= p; }

    Int128t operator*(const Int128t &p) const { return Int128t(*this) *= p; }

    Int128t operator/(const Int128t &p) const { return Int128t(*this) /= p; }

    Int128t operator%(const Int128t &p) const { return Int128t(*this) %= p; }

    bool operator<(const Int128t &a) const { return x < a.x; }

    bool operator>(const Int128t &a) const { return x > a.x; }

    bool operator<=(const Int128t &a) const { return x <= a.x; }

    bool operator>=(const Int128t &a) const { return x >= a.x; }

    bool operator==(const Int128t &a) const { return x == a.x; }

    bool operator!=(const Int128t &a) const { return x != a.x; }

    Int128t operator<<(const Int128t &a) const {
        return Int128t(x << a.x);
    }

    Int128t operator>>(const Int128t &a) const {
        return Int128t(x >> a.x);
    }

    Int128t& operator<<=(const Int128t &a) {
        x <<= a.x;
        return *this;
    }

    Int128t& operator>>=(const Int128t &a) {
        x >>= a.x;
        return *this;
    }
    
    friend istream &operator>>(istream &is, Int128t &x) {
        string s;
        is >> s;
        x.parse(s);
        return is;
    }

    friend ostream &operator<<(ostream &os, const Int128t &x) {
        if ( !ostream::sentry(os) ) return os;
        char buf[64];
        char *d = end(buf);
        __uint128_t tmp = (x.x < 0 ? -x.x : x.x);

        do {
            d--;
            *d = char(tmp % 10 + '0');
            tmp /= 10;
        } while ( tmp );
        if ( x.x < 0 ) {
            d--;
            *d = '-';
        }
        int len = end(buf) - d;
        if ( os.rdbuf()->sputn(d, len) != len ) { os.setstate(ios_base::badbit); }
        return os;
    }
};

using int128t = Int128t;

const int128t inf = 1e18;

void solve(){
    ll n,k,p;
    cin >> n >> p >> k;
    vector<vector<int128t>> dp(n+1,vector<int128t>(k+2,0));
    dp[0][0] = p;
    rep(i,n){
        ll t, b;
        cin >> t >> b;
        rep(j,k+1){
            if(dp[i][j] >= inf){
                pt(-1)
                return;
            }
            chmax(dp[i+1][j],dp[i][j]);
            if(t == 1){
                chmax(dp[i+1][j+1],dp[i][j]+b);
            }
            else{
                chmax(dp[i+1][j+1],dp[i][j]*2);
            }
        }
    }
    if(dp[n][k] >= inf){
        pt(-1)
        return;
    }
    pt(dp[n][k])
}

int main(){
    fast_io
    int t = 1;
    // cin >> t;
    rep(i,t) solve();
}