What does the following program output ?

#include  int f(int n) { if (n==0) return -2; if (n==1) return 0; if (n==2) return 1; return 2*f(n-1) - 4*f(n-2)+4*f(n-3); } int main() { int i=4; printf("%d ", f(i)); return 0; }