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

long long max(long long a,long long b){
    if(a>b){
        return a;
    }
    return b;
}

int main(){
    int K,N;
    long long P;
    cin >> N >> P >> K;
    int B,T;
    cin >> T >> B;
    long long dp[N][K+1];
    dp[0][0] = P;
    if(T == 1){
        dp[0][1] = P+B;
    }
    if(T == 2){
        dp[0][1] = 2*P;
    }
    for(int i=2;i<=K;i++){
        dp[0][i] = 0;
    }

    for(int i=1;i<N;i++){
        cin >> T >> B;
        for(int j=0;j<=K;j++){
            if(j > 0){
                if(T == 1){
                    dp[i][j] = max(dp[i-1][j],dp[i-1][j-1]+B);
                    if(dp[i-1][j] == -1 || dp[i-1][j-1] == -1 || dp[i][j] > 1000000000000000000){
                        dp[i][j] = -1;
                    }
                }
                if(T == 2){
                    dp[i][j] = max(dp[i-1][j],2*dp[i-1][j-1]);
                    if(dp[i-1][j] == -1 || dp[i-1][j-1] == -1 || dp[i][j] > 1000000000000000000){
                        dp[i][j] = -1;
                    }
                }
            } else {
                dp[i][j] = dp[i-1][j];
            }
        }
    }
    cout << dp[N-1][K] << endl;
}