521C

const
 inf = 1000000007;

var
  ans, sum, pr, suf, cnk1, cnk2, sfs, sf, z, z1: int64;
  a, fa: array[-100..100000] of int64;
  c: char;
  i, n, j, k: longint;


function f(i : int64): int64;// count i! here
var z : int64;
begin
  if fa[i]> 0 then f := fa[i] else
  begin
    if i <= 0 then z := 1
    else z := (int64(1)*f(i-1)*i)mod inf;
    fa[i] := z;
    f := z;
  end;
end;


begin

  read(n, k); //input begins
  readln;

  for i := 1 to n do
  begin
    read(c);
    val( c, a[i]);
    sum := sum + a[i];
  end;
  if k = 0 then
  begin
    for i := 1 to n do
      ans := (ans * 10 + a[i]) mod inf;
    writeln(ans);
    halt;
  end; // ends.


  sum := sum - a[1] - a[n];//in sum i sum all the numbers  of length(j) within range[2,..,n-1]

  sfs := sum; pr := a[1]; suf := a[n]; j := 1; z := 1;//sfs is a sum of a[j+1]+...+a[n-1]

  cnk1 := (f(n - j - 2) div f(k-2) div f(n - j - k))mod inf;// how many times we meet the numbers in a[2,..,n-1]
  cnk2 := (f(n - j - 1) div f(k-1) div f(n - j - k))mod inf;// how many times we meet the numbers on the borders of array
  ans := (ans + sum * cnk1 + (pr+suf) * cnk2)mod inf;// here will be the answer


  while j < n - k do
  begin
    inc( j );
    sfs := sfs - a[j];// update
    if (k = 0) then cnk1 := 0 else

    cnk1 := (f(n - j - 2) div f(k-2) div f(n - j - k))mod inf;//update
    cnk2 := (f(n - j - 1) div f(k-1) div f(n - j - k))mod inf;//update


    sf := (sf + z * a[n-j+1]) mod inf;//last number of length (j-1) in [2,..,n-1] range
    z  := (z * 10) mod inf;//when we add new digit to suffix, we multiple it by z( add j-1 zero)
    suf := (suf + z * a[n-j+1]) mod inf;//here is number on suffix of array
    sum := ((sum - sf) * 10 + sfs) mod inf;//updating sum
    pr  :=  (pr * 10 + a[j]) mod inf;//updating preffix
    ans := (ans + sum * cnk1 + (pr + suf) * cnk2) mod inf;
  end;


  writeln(ans);
end.