# 【題解】ZeroJudge a828: 間隔數 ( number )

```#include <iostream>
#include <cmath>
using namespace std;

int main(){
int num;
while (cin >> num){
num -= 1;
int count = -1, n = num % 81, a, b;
for (int i = 1; i < 10; i++){
for (int j = 0; j < 10; j++){
if (i != j){
count++;
}
if (count == n){
a = i;
b = j;
break;
}
}
if (count == n){
break;
}
}
n = (num / 81) + 3;
for (int i = 0; i < n; i++){
if (i % 2 == 0){
cout << a;
}else{
cout << b;
}
}
cout << "\n";
}
}
```

Python code (credit: Amy Chou)

```"""
N = ['10', '12', '13', '14', '15', '16', '17', '18', '19',
'20', '21', '23', '24', '25', '26', '27', '28', '29',
'30', '31', '32', '34', '35', '36', '37', '38', '39',
'40', '41', '42', '43', '45', '46', '47', '48', '49',
'50', '51', '52', '53', '54', '56', '57', '58', '59',
'60', '61', '62', '63', '64', '65', '67', '68', '69',
'70', '71', '72', '73', '74', '75', '76', '78', '79',
'80', '81', '82', '83', '84', '85', '86', '87', '89',
'90', '91', '92', '93', '94', '95', '96', '97', '98',]
"""
N = []
for i in range(1, 10):
for j in range(10):
if (i != j):
N.append(i*10 + j)

while True:
try:
n = int(input())
n -= 1
q = n // 81
p = n - q * 81
q += 3 # length of the output number

for i in range(q // 2):
print(N[p], end='')

if (q % 2 == 1):
print(N[p] // 10, end='')
print()

except:
break
```