function min(a, b, c, d: integer): integer;
begin
if (a <= b) and (a <= c) and (a <= d) then
min := a
else if (b <= a) and (b <= c) and (b <= d) then
min := b
else if (c <= a) and (c <= b) and (c <= d) then
min := c
else
min := d;
end;