private int ReverseModulus(int div, int a, int remainder)
{
if(remainder >= div)
throw new ArgumentException("Remainder cannot be greater than or equal to divisor");
if(a < remainder)
return remainder - a;
return div + remainder - a;
}
e.g. :
// (53 + x) % 62 = 44
var res = ReverseModulus(62,53,44); // res = 53
// (2 + x) % 8 = 3
var res = ReverseModulus(8,2,3); // res = 1