1)uses crt;
var n:string; t,a,b,i:longint;
begin
clrscr;
write('Nhap 1 so: ');readln(b);
str(b,n);
for i:=1 TO LENGTH(N) do begin val(n[i],a); inc(T,a); end;
writeln(t);
readln
end.
2)uses crt;
var n:string; b:longint;
begin
clrscr;
write('Nhap 1 so: ');readln(b);
str(b,n);
writeln(n);
readln
end.
3)uses crt;
var b,a:longint;
begin
clrscr;
write('Nhap 2 so: ');readln(a,b);
while a<>b do
if a>b then a:=a-b else b:=b-a;
writeln(a);
readln
end.
4)uses crt;
var a:longint;
Function nt(a:longint):boolean;
Var i:longint;
begin
i:=2;
while (a>1)and(a mod i<>0) do inc(i);
nt:=i=a;
end;
begin
clrscr;
write('Nhap 1 so: ');readln(a);
writeln(nt(a));
readln
end.
5)uses crt;
var i,n:longint;
Function nt(a:longint):boolean;
Var i:longint;
begin
i:=2;
while (a>1)and(a mod i<>0) do inc(i);
nt:=i=a;
end;
begin
clrscr;
write('Nhap n: ');readln(n);
for i:=1 to n do if nt(i) then writeln(i);
readln
end.