百度之星2014

include

include <stdio.h>

include <stdlib.h>

using namespace std;

int main()
{
int T;
scanf("%d",&T);
long long n,m,v,k;
while(T--)
{

cin>>n>>m>>v>>k;
int ans=0;
if(n<=m)
{
ans=0;
}else if( m <v || (m-v)k <= m) // k=0 0<= m
{
ans=-1;
}else {
while(n>m)
{
m= (m-v)k;
ans++;
}

}

printf("%d\n",ans);
}
return 0;
}