#include <stdio.h>
#include <stdlib.h>
#include <algorithm>

#define BUF_SIZE 16384
char buf[BUF_SIZE];
int pbuf=BUF_SIZE;
FILE*fi,*fo;
inline char nextch(){
    if(pbuf==BUF_SIZE){
        fread(buf, BUF_SIZE, 1, fi);
        pbuf=0;
    }
    return buf[pbuf++];
}
inline long long nextnum(){
    long long a=0;
    char c=nextch();
    while((c<'0' || c>'9') && c!='-')
        c=nextch();
    int semn=1;
    if(c=='-'){
        semn=-1;
        c=nextch();
    }
    while('0'<=c && c<='9'){
        a=a*10+c-'0';
        c=nextch();
    }
    return a*semn;
}

struct Oaie{
    long long d, a;
}v[100001];

int cmp(Oaie A, Oaie B){
    if(A.a>B.a) return 1;
    if(A.a<B.a) return 0;
    if(A.d>B.a) return 1;
    return 0;
}

int main(){
    fi=fopen("lupu.in","r");
    fo=fopen("lupu.out","w");
    int n=nextnum();
    long long x=nextnum(), l=nextnum();
    for(int i=0;i<n;i++){
        v[i].d=nextnum();
        v[i].a=nextnum();
    }
    std::sort(v, v+n, cmp);
    long long chosen=0;
    int ind=0;
    long long sum=0LL;
    while(ind<n){
        if(v[ind].d+chosen*l<=x){
            sum+=v[ind].a;
            chosen++;
        }
        ind++;
    }
    fprintf(fo,"%lld", sum);
    fclose(fi);
    fclose(fo);
    return 0;
}