GATE Computer Science (CS) 2016 Shift 2 Solved Paper

Consider the following program:
int f(int *p, int n)
{
             if(n <= 1) return 0;
             else return max (f(p + 1, n – 1), p[0] – p[1]);
}
int main()
{
int a[ ] = {3, 5, 2, 6, 4};
printf("%d", f(a,5));
}
Note: max(x, y) returns the maximum of x and y.
The value printed by this program is