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unable to explain how typecasting helps in getting proper value in add

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hi ,
please refer to the code below:


typedef unsigned char UInt8;
typedef unsigned short UInt16;
typedef unsigned long UInt32;
typedef unsigned long long UInt64;

int main(){
	UInt16 lowP = 8874, lowC =61008;
	UInt16 midP = 32566, midC =32848;
	UInt8 hiP = 0, hiC =0;

   //following two lines produce wrong output, note that we dont type cast midP and midC here
	UInt64 valP = lowP + (midP << 16) + (((unsigned long long)(hiP))<<32); //line 1
	UInt64 valC = lowC + (midC << 16) + (((unsigned long long)(hiC))<<32); //line 2

	//uncommenting below two lines instead of above two lines gives right result
   // UInt64 valP = lowP + (((unsigned long)midP) << 16) + (((unsigned long long)(hiP))<<32);
	//UInt64 valC = lowC + (((unsigned long)midC) << 16) + (((unsigned long long)(hiC))<<32);

	UInt64 diff = valC - valP;

	printf("valP:%x\n",valP >> 32); //print MSB 32 bits only
	printf("valC:%x\n",valC >> 32); //print MSB 32 bits only
	return 0;

now when I run this program I get following output:

However instead if I comment two lines mentioned as line1 and line2 and uncomment two lines
following in the code above, I get the following output:

Can somebody explain this behaviour?
Why sometimes I am getting 32bits MSB as all F sometimes though in code hiC is 0? And why timecasting micC to unsigned long
eradicate this problem?
I get most significant 32 bits as all F sometimes(for example with values in above code) when I dont typecast and I always get
as expected in case I typecast midC with unsigned long. Please explain.
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