How do you rewrite the following code using only 1 repetitive structure?

Question

for(int i=1; i<=n; i++){while(j<i){r=2*b-a; a=b; b=r; j=j+1}s=s+b}

Answer 1

It would help to know how j is initialized (what are its possible starting values?). Also answer the same question for a, b, s and n.

Answer 2

oops, sorry messed up a little, actually it is:
cin>>n;
s=0;
for(i=1; i<=n; i++){a=0; b=1; j=1;
while(j<i){r=2*b-a; a=b; b=r; j=j+1} s=s+b}
cout<<s;

Answer 3

The computation can be reduced to use only s and i in the for loop. To analyze, try inserting temporary cout statements to see the behavior of the variables - especially the outcome of b after the while loop.