#include <bits/stdc++.h>
using namespace std;
using ll=long long;
 
int main(){
    int n; cin>>n;
    const int MX=2005;
    ll dp[MX];
    fill(dp,dp+MX,LLONG_MIN);
    dp[0]=0;
 
    ll phoneMax=0; // 휴대폰 직접 연결 후보 최대 즐거움
    for(int i=0;i<n;i++){
        int a,b; cin>>a>>b;
        if(a==0){
            phoneMax=max(phoneMax,(ll)b);
        } else {
            for(int j=MX-1;j>=0;j--){
                if(dp[j]!=LLONG_MIN){
                    int nj=j+a-1;
                    nj=min(nj,MX-1);
                    dp[nj]=max(dp[nj],dp[j]+b);
                }
            }
        }
    }
 
    ll ans=LLONG_MIN;
    for(int i=0;i<MX;i++) ans=max(ans,dp[i]+phoneMax);
    cout<<ans<<"\n";
}

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15
1 -4034
1 3406
0 6062
4 -6824
0 9798
0 4500
0 -1915
1 2137
0 9786
0 7330
0 -9365
2 2730
0 -5797
0 6129
0 8925