Slalom

#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <vector>
#include <string>
#include <cctype>
#include <complex>
#include <cassert>
#include <utility>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
using namespace std;
typedef pair<int,int> PII;
typedef long long ll;
#define lson l,m,rt<<1
#define pi acos(-1.0)
#define rson m+1,r,rt<<11
#define All 1,N,1
#define N 1000010
#define read freopen("in.txt", "r", stdin)
const ll  INFll = 0x3f3f3f3f3f3f3f3fLL;
const int INF= 0x7ffffff;
const int mod =  1000000007;
int w,n,vh;
int x[N],y[N],s[N];
int solve(int v){
    double ll=x[0],rr=x[0]+w;
    for(int i=1;i<n;++i){
        double t=1.0*(y[i]-y[i-1])/v;
        ll-=t*vh;
        rr+=t*vh;
        if(ll>1.0*(x[i]+w)||rr<1.0*x[i])return 0;
        ll=max(ll,1.0*x[i]);
        rr=min(rr,1.0*x[i]+w);
    }
    return 1;
}
int main()
{
    int c,len;
    scanf("%d",&c);
    while(c--){
        scanf("%d%d%d",&w,&vh,&n);
        for(int i=0;i<n;++i)
            scanf("%d%d",&x[i],&y[i]);
        scanf("%d",&len);
        for(int i=1;i<=len;++i)
            scanf("%d",&s[i]);
        sort(s+1,s+len+1);
        int l=1,r=len,f=0,tmp;
        while(l<=r){
            int mid=(l+r)>>1;
            if(solve(s[mid])){
                tmp=mid;
                l=mid+1;
                f=1;
            }
            else r=mid-1;
        }
        if(f)
        printf("%d\n",s[tmp]);
        else printf("IMPOSSIBLE\n");
    }
return 0;
}