Weird bug in pointers

I was trying to access single bytes of an int value via the code below. My problem is that whenever I try to remove long int i=0; from the code, it gives me a segmentation fault. Is there any reason this happens? I am not using I anywhere in the code.

// Online C++ compiler to run C++ program online
#include <iostream>

int main() {
    // Write C++ code here
    
    unsigned int* a; 
    
    unsigned char* b1;
    unsigned char* b2; 
    unsigned char* b3; 
    unsigned char* b4;
    
    *a= 4294967295; //set to max val (4 bytes)
    //*************************
    long int i=0;//Q. Why long int/long long int? 
    //*************************
    
    b1 = (unsigned char*)(a);
    b2 = b1+(long long int)1;
    b3 = b1+(long long int)2;
    b4 = b1+(long long int)3;
    
    std::cout <<*a<<" "<<(int)*b1<<" "<<(int)*b2<<" "<<(int)*b3<<" "<<(int)*b4<<std::endl;
    
    
    return 0;
}

>Solution :

This exhibits undefined behavior:

unsigned int* a; 
*a= 4294967295; //set to max val (4 bytes)

The pointer variable a is never initialized to anything, so it points to a random memory address. Writing anything to that random garbage address (typically) causes a segmentation fault. It’s just coincidence that adding another variable changes the behavior (due to a change in memory layout of the program).