#include<bits/stdc++.h>

int n,id[],lp=;

double v1,v2,ans=1e10;

struct pos

{

    double x,y;

    void init(){scanf("%lf%lf",&x,&y);}

    pos operator+(pos a){return (pos){x+a.x,y+a.y};}

    pos operator-(pos a){return (pos){x-a.x,y-a.y};}

    pos operator*(double a){return (pos){x*a,y*a};}

    double operator*(pos a){return x*a.y-y*a.x;}

    double dot(pos a){return x*a.x+y*a.y;}

    double abs(){return sqrt(x*x+y*y);}

}ps[];

double mn,mx;

struct line

{

    pos a,b;

    void chk(line w)

     {

        double c=w.b*b;

        if(c==)return;

        c=(a*w.b+w.b*w.a)/c;

        if(c>0.5)c<mx&&(mx=c);

        else c>mn&&(mn=c);

     }

}ls[],l0[];

int main()

{

    scanf("%lf%lf%d",&v1,&v2,&n);

    for (int i=;i<=n;i++)ps[i].init(),id[i]=i;

    ps[n+]=ps[];

    pos p1=(pos){,},p2=(pos){v1,},p3=(pos){v1,v2},p4=(pos){,v2};

    ls[lp++]=(line){p1,p2-p1};

    ls[lp++]=(line){p2,p3-p2};

    ls[lp++]=(line){p3,p4-p3};

    ls[lp++]=(line){p4,p1-p4};

    for (int i=;i<=n;++i)l0[i]=(line){ps[i],ps[i+]-ps[i]};

    do

     {

        lp=;

        double s=;

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

         {

            int w=id[i];

            mn=-1e10,mx=1e10;

            for (int j=;j<lp;j++)l0[w].chk(ls[j]);

            ls[lp++]=l0[w];

            s+=(mx-mn)*l0[w].b.abs();

         }

        if (s<ans)ans=s;

     }while(std::next_permutation(id+,id+n+));

    printf("%.3f",ans);

    return ;

}