Given two strings, identify the string with the longest common substring.
hello = hallo
The longest common substring between the two strings "hello" and "hallo" is "allo" with 4 characters.
Complete the following task based on the instruction and optional input provided.### Instruction:
Given two strings, identify the string with the longest common substring.

### Input:
hello = hallo

### Output:
The longest common substring between the two strings "hello" and "hallo" is "allo" with 4 characters.