lst-0005-godb.cpp
//#(execute) c++; compiler:g132; options:-O3 -std=c++23; libs:-
// https://godbolt.org/z/Ex6Mv6xcz
unsigned fib(unsigned n) {
if(n==0) { return 0; }
if(n==1) { return 1; }
unsigned a = 0;
unsigned b = 1;
unsigned sum = 1;
while(n>1) {
sum += a;
a = b;
b = sum;
n -= 1;
}
return sum;
}