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uses clib;
var
n, i, j: int16;
m: int32 = 0;
a, b: array of int16;
procedure sort(l, h: int32);
var
i, j, k: int32;
tmp: int16;
begin
i := l;
j := h;
k := (l + h) div 2;
repeat
while a[i] * b[k] < a[k] * b[i] do
inc(i);
while a[j] * b[k] > a[k] * b[j] do
dec(j);
if i <= j then
begin
tmp := a[i];
a[i] := a[j];
a[j] := tmp;
tmp := b[i];
b[i] := b[j];
b[j] := tmp;
inc(i);
dec(j)
end
until i > j;
if l < j then
sort(l, j);
if i < h then
sort(i, h)
end;
begin
readln(n);
setlength(a, m);
setlength(b, m);
for i := 1 to n do
for j := 1 to n do
if gcd(i, j) = 1 then
begin
inc(m);
setlength(a, m);
a[m - 1] := i;
setlength(b, m);
b[m - 1] := j
end;
sort(0, m - 1);
writeln(m);
repeat
dec(m);
writeln(a[m], ' ', b[m])
until m = 0;
end.
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