#include <fstream>

using namespace std;
ifstream f("branza.in");
ofstream g("branza.out");
long long s,T,S,n,v[100001],c[100001],dq[100001];
int i,p,u;
int main()
{   f>>n>>S>>T;
    p=0;u=-1;
    for(i=1;i<=n;i++){
        f>>v[i]>>c[i];
        while(u>=p&&v[i]<=v[dq[u]]+(i-dq[u])*S)
            u--;
        dq[++u]=i;
        if(i-dq[p]>T)
            p++;
        s=s+v[dq[p]]*c[i]+S*(i-dq[p])*c[i];
    }
    g<<s;
    return 0;
}