#include<stdio.h>

int main()
{
	int a,b,sub;
	
	//input numbers
	printf("Enter first number: ");
	scanf("%d",&a);
	printf("Enter second number: ");
	scanf("%d",&b);
	
	//find subtraction using ~
	sub=a+~b+1;
	
	printf("subtraction of %d-%d=%d",a,b,sub);
	
	return 0;
}

Output

Enter first number: 10
Enter second number: 2
subtraction of 10-2=8

Here, sum = a+~b+1 i.e. variable a has its normal value, but the value of variable b is complemented i.e. '2' becomes '-3'.

a+~b+1= 10+(-3)+1=10-3+1=8.