# PROBLEM LINK:

* Author:* Adarsh Mandal

# DIFFICULTY:

EASY

# PREREQUISITES:

Math, Implementation

# EXPLANATION:

The key observation is that the digital root of an integer k is the single-digit number 1 ≤ d ≤ 9 such that k \equiv d \mod 9.

You can prove this by noticing that 10^p \equiv 1 \mod 9 for all p.

Once we observe this, finding the k-th number is very simple .

# SOLUTIONS:

## Setter's Solution

```
#include<bits/stdc++.h>
using namespace std;
#define ll long long
int main() {
int n;
cin >> n;
while (n--) {
ll k, x;
cin >> k >> x;
cout << (9 * (k - 1)) + x << endl;
}
}
```