#include<cstdio>
#include<algorithm>
#define N 15
#define db double
using namespace std;
int n;db c,d,x,y,ans;
struct node{db p,w;bool operator<(node y){return p<y.p;}}a[N];
int main()
{
    freopen("lyuxing.in","r",stdin);freopen("lyuxing.out","w",stdout);
    scanf("%lf%lf%lf%lf%d",&x,&c,&d,&y,&n);n+=2;c*=d;
    a[1]={0,y};a[n]={x,0};
    for(int i=2;i<n;i++)scanf("%lf%lf",&a[i].p,&a[i].w);
    sort(a+1,a+n+1);
    for(int i=1,j=1;j<n;j++)
    {
        if(a[j].w<a[i].w)i=j;
        if(a[j+1].p-a[j].p>c)return !printf("No Solution");
        ans+=(a[j+1].p-a[j].p)/d*a[i].w;
    }
    printf("%.2lf",ans);
    return 0;
}