Var
N:Byte;
Function RecFuc(N:Byte):Byte;
Begin
If N = 1 then RecFuc:=0
Else
If N = 2 then RecFuc:=1
Else
RecFuc:=RecFuc(N-1)+RecFuc(N-2)
End;
Begin
Readln(n);
Writeln(RecFuc(n));
Readln;
End.
Var
N:Byte;
Function RecFuc(N:Byte):Byte;
Begin
If N = 1 then RecFuc:=0
Else
If N = 2 then RecFuc:=1
Else
RecFuc:=RecFuc(N-1)+RecFuc(N-2)
End;
Begin
Readln(n);
Writeln(RecFuc(n));
Readln;
End.