#include <stdio.h>

void print_gray_reverse(int code[], int n, int index);

void print_gray(int code[], int n, int index);

void print_code(int code[], int len)

{

for(int i = 0; i < len; i++)

printf("%d",code[i]);

printf("\n");

}

void print_gray_reverse(int code[], int n, int index)

{

if(index == n) {

print_code(code, n);

return ;

}

code[index] = 1;

print_gray(code, n, index+1);

code[index] = 0;

print_gray_reverse(code,n,index+1);

}

void print_gray(int code[], int n, int index)

{

if(index == n) {

print_code(code, n);

return ;

}

code[index] = 0;

print_gray(code, n, index+1);

code[index] = 1;

print_gray_reverse(code,n,index+1);

}

void print_gray2(int code[], int n, int index, int reverse)

{

if(index == n) {

print_code(code, n);

return ;

}

code[index] = reverse;

print_gray2(code, n, index+1,0);

code[index] = 1 - reverse;

print_gray2(code,n,index+1,1);

}

#define MAXN 20

int main()

{

int code[MAXN], n;

printf("input n :");

scanf("%d",&n);

print_gray2(code,n,0,0);

return 0;

}