#include <bits/stdc++.h>
using namespace std;
using ll = long long;

struct stable_int{
    long long v;
    stable_int() : v(0) {}
    stable_int(long long _v) : v(_v){}
    stable_int& operator++() {
        if(__builtin_add_overflow(v, 1, &v))v = std::numeric_limits<long long>::max();
        return *this;
    }
    stable_int& operator--() {
        if(__builtin_sub_overflow(v, 1, &v))v = std::numeric_limits<long long>::min();
        return *this;
    }
    stable_int operator++(int) {
        stable_int result = *this;
        ++*this;
        return result;
    }
    stable_int operator--(int) {
        stable_int result = *this;
        --*this;
        return result;
    }
    stable_int& operator+=(const stable_int& rhs) {
        if(__builtin_add_overflow(v, rhs.v, &v))v = std::numeric_limits<long long>::max();
        return *this;
    }
    stable_int& operator-=(const stable_int& rhs) {
        if(__builtin_sub_overflow(v, rhs.v, &v))v = std::numeric_limits<long long>::min();
        return *this;
    }
    stable_int& operator*=(const stable_int& rhs) {
        long long pre = v;
        if(__builtin_mul_overflow(v, rhs.v, &v)){
            v = (pre > 0) ^ (rhs.v > 0) ? std::numeric_limits<long long>::min()
                                        : std::numeric_limits<long long>::max();
        }
        return *this;
    }
    stable_int& operator/=(const stable_int& rhs) {
        v /= rhs.v;
        return *this ; 
    }
    stable_int operator+() const { return *this; }
    stable_int operator-() const { return stable_int() - *this; }
    friend stable_int operator+(const stable_int& lhs, const stable_int& rhs) {
        return stable_int(lhs) += rhs;
    }
    friend stable_int operator-(const stable_int& lhs, const stable_int& rhs) {
        return stable_int(lhs) -= rhs;
    }
    friend stable_int operator*(const stable_int& lhs, const stable_int& rhs) {
        return stable_int(lhs) *= rhs;
    }
    friend stable_int operator/(const stable_int& lhs, const stable_int& rhs) {
        return stable_int(lhs) /= rhs;
    }
    friend bool operator==(const stable_int& lhs, const stable_int& rhs) {
        return (lhs.v == rhs.v);
    }
    friend bool operator!=(const stable_int& lhs, const stable_int& rhs) {
        return (lhs.v != rhs.v);
    }
    friend bool operator<(const stable_int& lhs, const stable_int& rhs) {
        return (lhs.v < rhs.v);
    }
    friend bool operator<=(const stable_int& lhs, const stable_int& rhs) {
        return (lhs.v <= rhs.v);
    }
    friend bool operator>(const stable_int& lhs, const stable_int& rhs) {
        return (lhs.v > rhs.v);
    }
    friend bool operator>=(const stable_int& lhs, const stable_int& rhs) {
        return (lhs.v >= rhs.v);
    }
    friend istream& operator>>(istream& is,stable_int& rhs) noexcept {
        long long _v;
        rhs = stable_int{(is >> _v, _v)};
        return is;
    }
    friend ostream& operator << (ostream &os, const stable_int& rhs) noexcept {
        return os << rhs.v;
    }
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll n, p, k;
    ll mx = 1'000'000'000'000'000'000ll;
    cin >> n >> p >> k;
    vector<stable_int> dp(k + 1, -mx);
    dp[0] = p;
    for(int i = 0; i < n; i++){
        ll t, b;
        cin >> t >> b;
        for(int j = k - 1; j >= 0; j--){
            if(t == 1) dp[j + 1] = max(dp[j + 1], dp[j] + b);
            else dp[j + 1] = max(dp[j + 1], dp[j] * 2);
        }
    }
    stable_int ans = dp[k];
    if(ans > mx) ans = -1;
    cout << ans << '\n';
}