bzoj3142

百度空间发公式太累，给个比较详细的解题链接吧
http://www.cnblogs.com/jianglangcaijin/archive/2013/08/13/3254314.html
注意M(k-1)<N是一个很重要的条件

 var n,m,ans,s:int64;
     p,k:longint;

 function quick(x:int64; y:longint):int64;
   begin
     quick:=;
     while y> do
     begin
       if y mod = then quick:=quick*x mod p;
       y:=y div ;
       x:=x*x mod p;
     end;
   end;

 begin
   readln(n,k,m,p);
   n:=n mod p;
   s:=quick(m mod p,k-);
   ans:=n*s mod p*m mod p-(m+)*m div  mod p*s mod p*int64(k-) mod p;
   writeln((ans+p) mod p);
 end.