Algo

program factoriel;
uses crt;
var
n,i:integer;
fact:real;
begin
repeat
writeln('entrer l"entier n');
readln(n);
until(n>=o);
if (n=0)or(n=1)then
begin
fact:=1;
end
else
begin
fact:=1;
for i:=1 to n do
begin
fact:=fact*i;
end;
end;
writeln('le factoriel de', n ,'est:',fact);
end.