USES
Crt;
VAR
x, n: INTEGER;
BEGIN
READLN(n);
REPEAT
x := 0;
REPEAT
x := x + n MOD 10;
n := n DIV 10
UNTIL n < 10;
n := x + n;
UNTIL n < 10;
WRITELN(n);
READLN
END.
USES
Crt;
VAR
x, n: INTEGER;
BEGIN
READLN(n);
REPEAT
x := 0;
REPEAT
x := x + n MOD 10;
n := n DIV 10
UNTIL n < 10;
n := x + n;
UNTIL n < 10;
WRITELN(n);
READLN
END.