수학

법칙을 찾으면 돼요. 그다음에 정답은요.
k^(m-1)*(n-(m-1)*k)+(m+(m-1)*k+1)*k^(m-1) div 2

/**************************************************************

    Problem: 3142

    User: BLADEVIL

    Language: Pascal

    Result: Accepted

    Time:0 ms

    Memory:224 kb

****************************************************************/

 

//By BLADEVIL

var

    n, m                    :int64;

    k, p, x                 :int64;

     

function mi(a,b:int64):int64;

var

    sum, ans                :int64;

begin

    sum:=a; ans:=1;

    while b>0 do

    begin

        if b mod 2=1 then ans:=ans*sum mod p;

        sum:=sum*sum mod p;

        b:=b div 2;

    end;

    exit(ans);

end;

begin

    readln(n,k,m,p);

    dec(k);

    x:=mi(m,k-1); 

    writeln(int64(n mod p*m-m*(m+1) div 2 mod p*k+p*1000000000) mod p*x mod p);

end.