1 const maxn=200419;
  2 var
  3  c,h,rank,sa,x,y,stack:array[0..maxn] of longint;
  4  n,k,top:longint;
  5  a,b,d:int64;
  6  s1,s2:ansistring;
  7
  8 function max(x,y:longint):longint; begin if x>y then exit(x) else exit(y); end;
  9 function min(x,y:longint):longint; begin if x<y then exit(x) else exit(y); end;
 10
 11 procedure make;
 12 var p,i,tot:longint;
 13 begin
 14  p:=1;
 15  while p<n do
 16   begin
 17    fillchar(c,sizeof(c),0);
 18    for i:= 1 to n-p do y[i]:=rank[i+p];
 19    for i:= n-p+1 to n do y[i]:=0;
 20    for i:= 1 to n do inc(c[y[i]]);
 21    for i:= 1 to n do inc(c[i],c[i-1]);
 22    for i:= 1 to n do
 23     begin
 24      sa[c[y[i]]]:=i;
 25      dec(c[y[i]]);
 26     end;
 27    fillchar(c,sizeof(c),0);
 28    for i:= 1 to n do x[i]:=rank[i];
 29    for i:= 1 to n do inc(c[x[i]]);
 30    for i:= 1 to n do inc(c[i],c[i-1]);
 31    for i:= n downto 1 do
 32     begin
 33      y[sa[i]]:=c[x[sa[i]]];
 34      dec(c[x[sa[i]]]);
 35     end;
 36    for i:= 1 to n do sa[y[i]]:=i;
 37    tot:=1;
 38    rank[sa[1]]:=1;
 39    for i:= 2 to n do
 40     begin
 41      if (x[sa[i]]<>x[sa[i-1]]) or (x[sa[i]+p]<>x[sa[i-1]+p]) then inc(tot);
 42      rank[sa[i]]:=tot;
 43     end;
 44    p:=p<<1;
 45   end;
 46  for i:= 1 to n do sa[rank[i]]:=i;
 47 end;
 48
 49 procedure makeh(s:ansistring);
 50 var i,j,p:longint;
 51 begin
 52  h[1]:=0; p:=0;
 53  for i:= 1 to n do
 54   begin
 55    p:=max(p-1,0);
 56    if rank[i]=1 then continue;
 57    j:=sa[rank[i]-1];
 58    while (i+p<=n) and (j+p<=n) and (s[i+p]=s[j+p]) do inc(p);
 59    h[rank[i]]:=p;
 60   end;
 61 end;
 62
 63 procedure init(s:ansistring);
 64 var i,tot:longint;
 65  ch:char;
 66 begin
 67  n:=length(s);
 68  for i:= 1 to n do c[i]:=0;
 69  for i:= 1 to n do x[i]:=ord(s[i]);
 70  for i:= 1 to n do inc(c[x[i]]);
 71  for i:= 1 to 122 do inc(c[i],c[i-1]);
 72  for i:= 1 to n do
 73   begin
 74    sa[c[x[i]]]:=i;
 75    dec(c[x[i]]);
 76   end;
 77  rank[sa[1]]:=1;
 78  tot:=1;
 79  for i:= 2 to n do
 80   begin
 81    if x[sa[i]]<>x[sa[i-1]] then inc(tot);
 82    rank[sa[i]]:=tot;
 83   end;
 84  fillchar(x,sizeof(x),0);
 85  fillchar(y,sizeof(y),0);
 86  make;
 87  makeh(s);
 88 end;
 89
 90 function calc(s:ansistring):int64;
 91 var ctb,i,m,ht,top:longint;
 92  ans:int64;
 93 begin
 94  ans:=0;
 95  init(s);
 96  h[0]:=k-1; h[n+1]:=k-1;
 97  top:=0; i:=1;
 98  stack[0]:=0;
 99  while i<=n+1 do
100   begin
101    ht:=h[stack[top]];
102    if ((h[i]<k) and (top=0)) or (h[i]=ht) then inc(i)
103     else if h[i]>ht then begin inc(top);stack[top]:=i; inc(i); end
104      else
105       begin
106        m:=i-stack[top]+1;
107        if (h[i]>=k) and (h[i]>h[stack[top-1]]) then
108         begin
109          ctb:=ht-h[i];
110          h[stack[top]]:=h[i];
111         end
112        else
113         begin
114          ctb:=ht-h[stack[top-1]];
115          dec(top);
116         end;
117        inc(ans,(int64(m)*int64(m-1) div 2) *int64(ctb));
118       end
119   end;
120  exit(ans);
121 end;
122
123 Begin
124  readln(k);
125  while k<>0 do
126   begin
127    readln(s1);
128    a:=calc(s1);
129    readln(s2);
130    b:=calc(s2);
131    s1:=s1+'$'+s2;
132    d:=calc(s1);
133    writeln(d-a-b);
134    readln(k);
135   end;
136 End.