BoB

#include <cstdio>
#include <cctype>
#include <algorithm>
using namespace std;
struct ELEM
{
    int x,y;
};
int g[300005],val[300005];
long long BITree[300005];
int _in_loc;
char _in_buff[4096];
ELEM vals[300005];
int uniqueArr[300005];

bool cmp(ELEM a,ELEM b)
{
    return a.x<b.x;
}
char read_ch()
{
    ++_in_loc;
    if (_in_loc == 4096) {
        _in_loc = 0;
        fread(_in_buff, 1, 4096,stdin);
    }
    return _in_buff[_in_loc];
}

int read()
{
    int u32 = 0; char c;
    while (!isdigit(c = read_ch()) );
    u32 = c - '0';
    while (isdigit(c = read_ch())) {
        u32 = u32 * 10 + c - '0';
    }
    return u32;
}
inline long long getSum(int index)
{
    long long  sum = 0;
    while (index > 0) {
        if(sum<BITree[index])
            sum=BITree[index];
        index -= index & (-index);
    }
    return sum;
}
inline void updateBIT(int newIndex,int index,long long val)
{
    while (index <= newIndex) {
        if(val>BITree[index])
            BITree[index]=val;
        index += index & (-index);
    }
}
inline long long resolve(int n)
{
    int newindex = 0;
    long long max_sum;
    for (register int i = 0; i < n; i++) {
        vals[i].x=g[i];
        vals[i].y=i;
    }
    sort(vals,vals+n,cmp);
    for(register int i=0;i<n;++i)
    {
        if(vals[i].x==vals[i-1].x)
            uniqueArr[vals[i].y]=uniqueArr[vals[i-1].y];
        else
            uniqueArr[vals[i].y]=++newindex;
    }
    for (register int i = 0; i < n; i++) {
        max_sum = getSum(uniqueArr[i] - 1);
        updateBIT(newindex, uniqueArr[i], max_sum + val[i]);
    }
    return getSum(newindex);
}

int main()
{
    int n;
    scanf("%d",&n);
    _in_loc = 4095;
    for(register int i=0;i<n;++i)
    {
        g[i]=read();
        val[i]=read();
    }
    printf("%lld\n",resolve(n));
    return 0;
}