Write a function `decimal_to_binary(n)` that takes an integer `n` as input and returns its binary equivalent as a string without leading zeros. The function should handle non-negative integers only.
#### Example Usage
```python [main.nopy]
print(decimal_to_binary(8)) # Output: '1000'
print(decimal_to_binary(18)) # Output: '10010'
print(decimal_to_binary(7)) # Output: '111'
```
#### Constraints
- The input `n` will be a non-negative integer.
- The output should be a string representing the binary equivalent of the input number.