Author

  var
    fr,fw:text;
    n,m:integer;
    s,w:string;
    ma:array[1..101,1..101] of integer;

  var
    wp:array[1..101] of integer;
  procedure prepare;
  var i,j,wl:integer;
      si:char;
  begin
    FillChar(wp,sizeof(wp),0);
    wl:=length(w);
    if wl>1 then
    begin
      for i:=1 to n do
        begin
          si:=s[i];
          if (wp[wl]>0)and(w[wl]=si) then
            begin
            if (ma[wp[wl],i+1]=-1)or(ma[wp[wl],i+1]>wl-wp[wl]-i-1) then
              ma[wp[wl],i+1]:=i+1-wp[wl]-wl;
            end;
          for j:=wl-1 downto 2 do
            if (wp[j]>0)and(w[j]=si) then
              begin
                wp[j+1]:=wp[j];
                wp[j]:=0;
              end;
          if w[1]=si then wp[2]:=i;
        end;
    end else
    begin
      for i:=1 to n do
        if s[i]=w[1] then
          begin
            ma[i,i+1]:=0;
          end;
    end;
  end;

  var d,u:array[1..101] of integer;
  procedure find_way(start:integer);
  var i,j:integer;
      dmin,darg:integer;
  begin
    for i:=start+1 to n+1 do d[i]:=102;
    d[start]:=0;
    fillChar(u,sizeof(u),0);
    while true do
      begin
        dmin:=102;
        darg:=n+1;
        for j:=start to n+1 do
          if (u[j]=0)and(dmin>d[j]) then
            begin
              dmin:=d[j];
              darg:=j;
            end;
        if darg=n+1 then break;
        u[darg]:=1;
        for j:=start+1 to n+1 do
          if (u[j]=0)and
          (ma[darg,j]>-1)and
          (d[darg]+ma[darg,j]<d[j]) then
            d[j]:=d[darg]+ma[darg,j];
      end;
  end;

  procedure Make;
  var i:integer;
      res:integer;
  begin
    find_way(1);
    res:=d[n+1];
    writeln(fw,res);
  end;

  var
    i:integer;
begin
  assign(fr,'cipher.dat');
  reset(fr);
  assign(fw,'cipher.sol');
  rewrite(fw);
  readln(fr,n,m);
  readln(fr,s);

  FillChar(ma, sizeof(ma), 255);
  for i:=1 to n do
    begin
      ma[i,i+1]:=1;
    end;
  for i:=1 to m do
    begin
      readln(fr,w);
      prepare;
    end;

  Make;

  close(fr);
  close(fw);
end.