Hello, strange, so strange, I am still think it is 0 not 4

1.public int Evaluate(s,t){
2.{
3.if(s==0 || t==0)
4.return 0;
5.}
6.else if{
7.y=Evaluate(s,t-1); // this
8.return s+y;
9.}
10.}

Line 7 rerun line 1, so no value is put for y
t=2-1=1
s=2
line 3 checks t and s
unsatisfactorily, line 6 come again, line 7 again rerun line 1, still no value for y
t=1-1=0
s=2
Now t=0
line 2-3 checks t=0 so satisfied it returns 0

So the final result is 0, line 8 never reaches

Answer=0

Am I right ?