#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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4 -6824
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0 -1915
1 2137
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0 7330
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2 2730
0 -5797
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