#include <iostream>

using namespace std;

const int MAXN = 52;

double dis[MAXN], D;

double price[MAXN];

int K;

double ans;

const double INF = 99999999;

double mpg, cost_original, g_p;

bool dfs(double cur_dis, int cur_pos, double money, double gas){

if(cur_pos == K){

ans = min(ans, money);

return true;

}

cout<<"now at "<<cur_pos<<" money is "<<money<<" "<<gas<<endl;

for(int i=cur_pos+1; i<=K; i++){

if(gas*mpg>= dis[i] - cur_dis){

double gas_left = gas - (dis[i]-cur_dis)/mpg;

if(gas_left < g_p/2 || (gas_left>g_p/2 && i+1<=K-1 && gas_left*mpg<dis[i+1]-dis[i])){

dfs(dis[i], i, money+(g_p-gas)*price[i]+200, g_p);

}

/*

if(gas_left > g_p/2 ){

if((i+1<=K-1 && gas_left*mpg<dis[i+1]-dis[i])){

}

}

*/

}

}

}

void work(){

ans = INF;

dfs(0,-1, cost_original*100, g_p);

cout<<ans<<endl;

}

int main(){

while(cin>>D){

cin>>g_p>>mpg>>cost_original>>K;

for(int i=0; i<K; i++){

cin>>dis[i]>>price[i];

}

price[K] = 0, dis[K] = D;

work();

}

return 0;

}