#include<cstdio>
#include<algorithm>
#include<cmath>
#include<iostream>
#include<set>
#include<vector>
#include<queue>
#include<stack>
#include<cstring>
#include<cstdlib>
#include<ctime>
#define rep(i,a,b) for(register int i=a;i<=b;++i)
#define rev(i,a,b) for(register int i=a;i>=b;--i)
#define gra(i,u) for(register int i=head[u];i;i=edge[i].nxt)
#define Clear(a) memset(a,0,sizeof(a))
#define yes puts("YES")
#define no puts("NO")
using namespace std;
typedef long long ll;
const int INF(1e9+10);
const ll LLINF(1e18+10);
inline int read()
{
    int s=0,w=1;
    char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
    while(ch>='0'&&ch<='9')s=s*10+(ch-'0'),ch=getchar();
    return s*w;
}
template<typename T>
inline T Min(T x,T y){return x<y?x:y;}
template<typename T>
inline T Max(T x,T y){return x>y?x:y;}
template<typename T>
inline void Swap(T&x,T&y){T t=x;x=y;y=t;return;}
template<typename T>
inline T Abs(T x){return x<0?-x:x;}

const int MAXN(2010);

int n;
int a[MAXN],b[MAXN],s[MAXN],f[MAXN];
int gou,ans,tot;

inline bool cmp(int x,int y){return x>y;}

int main()
{
    // freopen("read3.txt","r",stdin);
    n=read();
    rep(i,1,n) a[i]=read(),b[i]=read();
    gou=1;
    rep(i,1,n)
    {
    	if(a[i]>=1&&b[i]>=0) gou+=a[i]-1,ans+=b[i];
    	else if(a[i]==0&&b[i]>=0) s[++tot]=b[i];
    }
    sort(s+1,s+1+tot,cmp);
    rep(i,1,tot) s[i]+=s[i-1];
  	memset(f,~0x3f,sizeof(f));
  	rep(i,0,gou) f[i]=ans;
  	rep(i,1,n) if(a[i]>=1&&b[i]<0) rev(j,2000,a[i]+gou-1) f[j]=Max(f[j],f[j-a[i]+1]+b[i]);
  	int res(0);
  	rev(i,n-1,1) f[i]=Max(f[i+1],f[i]); 
  	rep(i,0,2000) res=Max(res,f[i]+s[i]);
  	printf("%d\n",res);  
    return 0;
}
/*
Date : 2022/9/27
Author : UperFicial
Start coding at : 20:44
finish debugging at :
*/