#include<bits/stdc++.h>
#define cir(i,a,b) for(int i=a;i<b;++i)
using namespace std;
ifstream fcin("wind.in");
ofstream fcout("wind.out");
class fileio{
public:
    ~fileio(){
        fcin.close();fcout.close();
    }
} use_fileio;
using lint=long long;
using qint=__int128_t;
static constexpr auto _infl=(lint)(1e18l);
auto&operator>>(istream&is,qint&x){
    string s;is>>s;x=0;auto sgn=1;
    if(s[0]=='-') sgn=-sgn,s.erase(s.begin());
    for(auto&w:s) (x*=10)+=(w-'0');
    x*=sgn;
    return is;
}
constexpr auto abs(qint x){return x<0?-x:x;}
int main(){
    ios::sync_with_stdio(false),fcin.tie(nullptr);
    int T;fcin>>T;
    while(T--) [&]{
        int n;qint k,x,y;fcin>>n>>k>>x>>y;
        vector<qint> a(n),b(n);
        cir(i,0,n) fcin>>a[i]>>b[i];
        const auto suma=accumulate(a.begin(),a.end(),(qint)(0));
        const auto sumb=accumulate(b.begin(),b.end(),(qint)(0));
        auto ans=_infl;
        auto vaild=[&](const auto cx,const auto cy,const auto w){
            if(!k) return !(abs(cx-x)+abs(cy-y));
            return (abs(cx-x)+abs(cy-y)+k-1)/k<w+1;
        };
        auto check=[&](const auto c){
            auto prea=(qint)(0),preb=(qint)(0);
            cir(i,0,n) if(vaild(suma*c+prea,sumb*c+preb,(lint)(c)*n+i)){
                ans=min(ans,(lint)(c)*n+i);
                return true;
            }else{
                prea+=a[i];preb+=b[i];
            }
            return false;
        };
        check(0);
        auto l=1,r=(int)(1e9+7);
        while(l-1<r){
            const auto mid=(l+r)/2;
            check(mid)?(r=mid-1):(l=mid+1);
        }
        fcout<<(ans<_infl?ans:-1)<<'\n';
    }();
    return 0;
}