#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
const int N = 2e3 + 5;
long long n,dp[N][N],rmq[N][20];
pair<long long,long long> rope[N];
long long get(int l,int r){
int k = log2(r - l + 1);
return max(rmq[l][k], rmq[r-(1<<k)+1][k]);
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n;
for(int i=1;i<=n;i++) cin >> rope[i].fi >> rope[i].se;
for(int i=0;i<=n;i++){
for(int j=1;j<=n;j++){
dp[i][j] = -1e18;
}
}
sort(rope+1, rope+1+n);
for(int i=0;i<=n;i++) rmq[i][0] = dp[0][i];
for(int j=1;(1<<j)<=n;j++){
for(int i=0;i+(1<<j)-1<=n;j++){
rmq[i][j] = max(rmq[i][j-1], rmq[i+(1<<(j-1))][j-1]);
}
}
for(int i=1;i<=n;i++){
for(int j=1;j<=i;j++){
dp[i][j] = get(j - 1, min(n, j + rope[i].fi - 1)) + rope[i].se;
dp[i][j] = max(dp[i][j], dp[i-1][j]);
}
for(int j=0;j<=n;j++){
rmq[j][0] = dp[i][j];
}
for(int k=1;(1<<k)<=n;k++){
for(int j=0;j+(1<<k)-1<=n;j++){
rmq[j][k] = max(rmq[j][k-1], rmq[j+(1<<(k-1))][k-1]);
}
}
}
cout << max(dp[n][0], dp[n][1]);
}
