#include <bits/stdc++.h>
#define il inline
#define ll __int128
using namespace std;
#define pii pair<ll,ll>
#define fi first
#define se second
il ll read(){
    ll x=0,f=0,c=getchar();
    while(!isdigit(c)) f|=c=='-',c=getchar();
    while(isdigit(c)) x=x*10+c-48,c=getchar();
    return f?-x:x;
}
void write(ll x){
    if(x>9) write(x/10);
    putchar(x%10+48);
}
il void print(ll x,char c){write(x),putchar(c);}
il ll ab(ll x){return x>0?x:-x;}
il int in(ll x,ll l,ll r){return x>=l && x<=r;}
const int N=1e5+5;const ll inf=1e18,oo=1e18;
il pii solve(ll u,ll v){//u*x>=v qujian
    if(!u){
        if(v<=0) return {-oo,oo};
        else return {oo,-oo};
    }
    ll x;
    if(u<0){
        x=v/u;while(x*u<v) --x;
        return {-oo,x};
    }
    else{
        x=v/u;while(x*u<v) ++x;
        return {x,oo};
    }
}
il pii jiao(pii u,pii v){return {max(u.fi,v.fi),min(u.se,v.se)};}
int T,n,k;ll s,t,a[N],b[N],s1[N],s2[N],A,B,ans;
ll x,y,z;
il int ck1(ll u,int i){
    ll m=ll(1)*n*u+i;
    return in(s+t-(A+B)*u-(x+y),-ll(1)*m*k,ll(1)*m*k);
}
il int ck2(ll u,int i){
    ll m=ll(1)*n*u+i;
    return in(s-t-(A-B)*u-(x-y),-ll(1)*m*k,ll(1)*m*k);
}
pii c1,c2,c3,c4,ret;ll u,v,w;
int main(){
    //freopen("wind.in","r",stdin);
    //freopen("wind.out","w",stdout);
    scanf("%d",&T);
    while(T--){
        n=read(),k=read(),s=read(),t=read();
        for(int i=0;i<n;++i) a[i]=read(),b[i]=read();
        s1[0]=1ll*a[0],s2[0]=1ll*b[0];
        for(int i=1;i<n;++i) s1[i]=s1[i-1]+ll(1)*a[i],s2[i]=s2[i-1]+ll(1)*b[i];
        if(!s && !t){puts("0");continue;}
        x=y=0ll,A=s1[n-1],B=s2[n-1],ans=oo;
        for(int i=0;i<n;++i){//m%n;
            if(in(s-x+t-y,-ll(1)*i*k,1ll*i*k) && in(s-x-t+y,-ll(1)*i*k,ll(1)*i*k)){
                ans=min(ans,ll(i));
                x+=ll(1)*a[i],y+=ll(1)*b[i];
                continue;
            }
            c1=c2=c3=c4={-oo,oo};
            u=ll(1)*n*k-(A+B),v=x+y-ll(1)*i*k-(s+t);
            c1=solve(u,v);
            u=(A+B+ll(1)*n*k),v=s+t-(x+y)-ll(1)*i*k;
            c2=solve(u,v);
            u=ll(1)*n*k-(A-B),v=(x-y)-ll(1)*i*k-(s-t);
            c3=solve(u,v);
            u=ll(1)*n*k+(A-B),v=(s-t)-(x-y)-ll(1)*i*k;
            c4=solve(u,v);
            ret=jiao(jiao(c1,c2),jiao(c3,c4));
            if(ret.fi<=ret.se && ret.se>=ll(0)) ans=min(ans,max(ll(0),ret.fi)*ll(1)*n+i);
            x+=1ll*a[i],y+=ll(1)*b[i];
        }
        if(ans==oo) puts("-1");
        else print(ans,'\n');
    }
    return 0;
}