#include <bits/stdc++.h>

using namespace std;

int c[100010];
deque<int>d;
int n,s,t,i,x,y;

long long total;

int main()
{
    freopen("branza.in","r",stdin);
    freopen("branza.out","w",stdout);
    scanf("%d%d%d",&n,&s,&t);
    for (i=1;i<=n;i++){
        scanf("%d%d",&x,&y);
        c[i]=x;
        while (!d.empty()&&(c[d.back()]+s*(i-d.back())>c[i])) d.pop_back();
        d.push_back(i);
        while (i-d.front()>t&&!d.empty()) d.pop_front();
        total+=1LL*(c[d.front()]+s*(i-d.front()))*y;
    }
    printf("%lld",total);
    return 0;
}