C :

#include<stdio.h>
int main()
{
    int t,k,a,b,v,x,y,c,ans;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d%d%d%d",&k,&a,&b,&v);
        x=a/v;
        if(a%v) x++;
        c=x/k*(k-1);
        if(x%k) c+=x%k-1;
        if(c<=b)
        {
            ans=x/k;
            if(x%k) ans++;
        }
        else
        {
            ans=x-b/(k-1)*(k-1);
            if(b%(k-1))
                ans-=b%(k-1);
        }
        printf("%d\n",ans);
    }
    return 0;
}

C++ :

#include<stdio.h>
int main()
{
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    int k,a,b,v,t;
    scanf("%d",&t);
    while(t--)
    {   scanf("%d%d%d%d",&k,&a,&b,&v);
        int ans=0,box=0,kk=k-1;
        while(ans<a)
        {
            if(b>=kk)
            {
                ans+=v*k;
                b-=kk;
                box++;
            }
            else if(b>0)
            {
                ans+=(b+1)*v;
                b=0;
                box++;
            }
            else if(b==0)
            {
                ans+=v;
                box++;
            }
        }
        printf("%d\n",box);
    }
    return 0;
}