#!/bin/python3

import os


def acessoryCollection(L, A, N, D):
    if D > A or N < D or N > L: return "SAD"
    elif D == 1: return str (L * A)
    else:
        max = 0
        a2Max = (N - 1) // (D - 1)
        for a2 in range (a2Max, 0, -1):
            a1 = N + (a2 - 1) - a2 * (D - 1)
            n = (L - a1) // a2
            a3 = (L - a1) % a2
            if n > A - 1 or n == A - 1 and a3 > 0: break
            sum = A * a1 + (A - 1 + A - n) * n // 2 * a2 + a3 * (A - n - 1)
            if sum <= max: break
            max = sum
        if max: return str (max)
        else: return "SAD"

if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')

    T = int(input())

    for T_itr in range(T):
        LAND = input().split()

        L = int(LAND[0])

        A = int(LAND[1])

        N = int(LAND[2])

        D = int(LAND[3])

        result = acessoryCollection(L, A, N, D)

        fptr.write(result + '\n')

    fptr.close()

string acessoryCollection(int L, int A, int N, int D) {
    long long ans=0;
    if(N<D) ans=-1;
    else if(D==1){
        ans=L*A;
    }
    else{ 
        int min=N-D+1;
        while(L>min){
            if(A==0) {
                ans=-1;
                break;
            }
            ans+=min*A;
            A--;
            L-=min;
        }
        if(L>0 & A==0) ans=-1;
        else if(L>0) ans+=L*A;
    }
    //cout << ans<<endl;
    string str;
    while(ans>0){
        str.push_back('0'+ans%10);
        ans=ans/10;
    }
    if(str.size()!=0){
        reverse(str.begin(),str.end());
    }
    
    if(ans==-1) return "SAD";
    else return str;
    
 
}