#include <cstdio>
#include <algorithm>

using namespace std;
pair <long long,long long> v[50001],h[50001];
int elem;
int compar (long long a,long long b){
    int x,y,z,t;
    x=h[a].first;
    y=h[a].second;
    z=h[b].first;
    t=h[b].second;
    return (x*t>z*y);
}
void adauga (long long a,long long b){
    long long p,c;
    elem++;
    h[elem].first=a;
    h[elem].second=b;
    c=elem;
    p=elem/2;
    while (p>0){
        if (compar (c,p))
            swap (h[c],h[p]);
        else break;
        c=p;
        p/=2;
    }
}
void sterge (long long poz){
    long long p,c;
    h[poz].first=h[elem].first;
    h[poz].second=h[elem].second;
    elem--;
    p=poz;
    c=2*poz;
    while (c<=elem){
        if (c+1<=elem && h[c+1]>h[c])
            c++;
        if (compar (c,p))
            swap (h[c],h[p]);
        else break;
        p=c;
        c*=2;
    }
}
int main()
{
    FILE *fin=fopen ("peste.in","r");
    FILE *fout=fopen ("peste.out","w");
    long long n,k,t,s,sol,dr,i;
    fscanf (fin,"%lld%lld%lld",&n,&k,&t);
    for (i=1;i<=n;i++)
        fscanf (fin,"%lld%lld",&v[i].second,&v[i].first);
    sort (v+1,v+n+1);
    s=0;
    for (i=n;n-i+1<=k;i--)
        s+=v[i].second;
    adauga (s,v[n].first);
    dr=n;
    for (;i>0;i--){
        s-=v[dr].second;
        s+=v[i].second;
        dr--;
        adauga (s,v[dr].first);
    }
    sol=0;
    while (elem){
        if (t-h[1].second>=0){
            t-=h[1].second;
            sol+=h[1].first;
        }
        else sterge (1);
    }
    fprintf (fout,"%lld",sol);
    return 0;
}