#include<cstdio>

#include<cstring>

#include<algorithm>

using namespace std;

const int maxn=;

typedef double dd;

struct node

{

    dd p,dis;

}s[maxn];

dd all_dis,capa,per_dis,st_p;

int n;

bool cmp(node qw,node we)

{

    return qw.dis<we.dis;

}

dd ans_cost,last;

int main()

{

    scanf("%lf%lf%lf%lf%d",&all_dis,&capa,&per_dis,&st_p,&n);

    s[].p=st_p;

    for(int i=;i<=n;i++)

    {

        scanf("%lf%lf",&s[i].dis,&s[i].p);

    }

    s[n+].dis=all_dis;

    for(int i=;i<=n;i++)

    {

        if(s[i+].dis-s[i].dis>capa*per_dis)

        {

            printf("No Solution\n");

            return ;

        }

    }

    sort(s+,s+n+,cmp);

    for(int i=;i<=n+;)

    {

        int j,k;

        for(j=k=i+;j<=n;j++)

        {

            k=(s[j].p<=s[k].p?j:k);

            if(s[j].p<=s[i].p||(s[j+].dis-s[i].dis)>capa*per_dis) break;

        }

        if(s[j].p>s[i].p)

        {

            ans_cost+=(capa-last)*s[i].p;

            last=capa-((s[k].dis-s[i].dis)/per_dis);

            i=k;

        }

        else

        {

            ans_cost+=((s[j].dis-s[i].dis)/per_dis-last)*s[i].p;

            last=;

            i=j;

        }

    }

    printf("%.2lf",ans_cost);

    return ;

}