The function realloc(ptr,n) uses two arguments.the first argument ptr is a pointer to a block of
memory for which the size is to be altered. The second argument n specifies the new size.
The size may be increased or decreased. If n is greater than the old size and if sufficient
space is not available subsequent to the old region, the function realloc( ) may create a new
region and all the old data are moved to the new region.