#include <bits/stdc++.h>
using namespace std;
#define maxn 100000
#define db double
#define INF 9999999
int n;
db D1, D2, C, P, res, ans, maxx;
struct node
{
db co, dis;
bool friend operator <(const node& a, const node& b)
{ return a.dis < b.dis; }
}pl[maxn];
int Solve(int now)
{
int flag = INF; db d = pl[now].dis;
for(int i = now + 1; i <= n && pl[i].dis - d <= maxx; i ++)
{
if(pl[i].co < pl[now].co)
{
ans += ((pl[i].dis - d - res) / D2) * pl[now].co;
res = 0; return i;
}
if(flag == INF || pl[i].co < pl[flag].co) flag = i;
}
if(D1 - pl[now].dis <= maxx)
{
ans += ((D1 - pl[now].dis - res) / D2) * pl[now].co;
return INF;
}
if(flag == INF) { printf("No Solution\n"); return -1; }
else
{
ans += C * pl[now].co; res += (maxx - (pl[flag].dis - d));
return flag;
}
}
int main()
{
scanf("%lf%lf%lf%lf%d", &D1, &C, &D2, &P, &n);
pl[0].dis = 0, pl[0].co = P;
for(int i = 1; i <= n; i ++)
scanf("%lf%lf", &pl[i].dis, &pl[i].co);
sort(pl, pl + n + 1);
maxx = C * D2;
int k = 0, t;
do
{
t = Solve(k), k = t;
if(t == -1) return 0;
}while(t != INF);
printf("%.2lf", ans);
return 0;
}
