#include<queue>
#include<math.h>
#include<stdio.h>
#include<iostream>
#include<vector>
#include<iomanip>
#include<string.h>
#include<algorithm>
#include<cmath>
#include<cstdio>
#include<utility>
#include<cstring>
#include<stack>
#include<fstream>
#include<string>
using namespace std;
#define LL long long
const int N = 1e4 + 10;
const int INF = 0x3f3f3f3f;
double maxx,mo=0,d2,temlen=0,d1,c,p;
int n;
struct add
{
    double co;
    double dis;
}pl[10000];
int move(int now)
{
    int can=99999;
    int f=pl[now].dis;
    for(int i=now+1;i<=n&&pl[i].dis-f<=maxx;i++)
    {
        if(pl[i].co<pl[now].co)
        {
            mo+=((pl[i].dis-f-temlen)/d2)*pl[now].co;
            temlen=0;
            return i;
        }
        if(can==99999||pl[i].co<pl[can].co)can=i;
    }
    if(d1-pl[now].dis<=maxx)
        {
            mo+=((d1-pl[now].dis-temlen)/d2)*pl[now].co;
            return 9999;
        }
    if(can==99999)
    {
        cout<<"No Solution";
        return -1;
    }
    else
    {
        mo+=c*pl[now].co;
        temlen+=(maxx-pl[can].dis+f);
        return can;
    }
}
int cmp(add a,add b)
{
    return a.dis<b.dis;
}
int main()
{
    cin>>d1>>c>>d2>>p>>n;
    pl[0].dis=0;
    pl[0].co=p;
    for(int i=1;i<=n;i++)cin>>pl[i].dis>>pl[i].co;
    sort(pl,pl+n,cmp);
    maxx=c*d2;
    int k=0,t;
    do
    {
        t=move(k);
        k=t;
        if(t==-1)return 0;
    }while(t!=9999);
    printf("%.2f",mo);
    return 0;
}