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;

}