POLANN_3

Var
    X: Array [1..25] Of LongInt;
    Y: Real; I: Integer;

Function CalcLevel(ALev: Integer): Real;
Var
    Z: Real; I, S: Integer;
Begin
    S:= -1;
    Z:= X[25];
    For I:= 24 DownTo ALev Do Begin
        Z:= Z + X[I] * S;
        S:= -S;
    End;
    CalcLevel:= Z;
End;

Begin
    WriteLn('Введите массив X:');
    For I:= 1 To 25 Do Begin
        Write('X[', I, '] = ');
        ReadLn(X[I]);
    End;
    Y:= X[25] * 25;
    For I:= 24 DownTo 1 Do Y:= Y * CalcLevel(I);
    WriteLn('Y = ', Y);
    ReadLn;
End.