C11PINES - Growing Pines

Tác giả: ladpro98

Ngôn ngữ: Pascal

program c11pines;
uses    math;
const   fi='';
        maxN=12345;
var     a:array[1..maxN] of longint;
        n,d:longint;
        res:int64;

procedure input;
var     inp:text;
        i:longint;
begin
        assign(inp,fi);
        reset(inp);
        readln(inp,n,d);
        for i:=1 to n do
        read(inp,a[i]);
        close(inp);

end;

procedure swap(i,j:longint);
var     t:longint;
begin
        t:=a[i];
        a[i]:=a[j];
        a[j]:=t;
end;

procedure sort(l,r:longint);
var     i,j,p:longint;
begin
        if l>=r then exit;
        p:=a[random(r-l+1)+l];
        i:=l;j:=r;
        repeat
                while a[i]<p do inc(i);
                while a[j]>p do dec(j);
                if i<=j then
                begin
                        if i<j then swap(i,j);
                        inc(i);dec(j);
                end;
        until i>j;
        sort(l,j);sort(i,r);
end;

procedure process;
var     i,modul:longint;
begin
        modul:=a[1] mod d;
        for i:=2 to n do
        if a[i] mod d<>modul then
        begin
                res:=-1;
                exit;
        end;
        res:=0;
        for i:=2 to n do
        res:=res+(a[i]-a[1]) div d;

end;

begin
        input;
        sort(1,n);
        process;
        write(res);
end.

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