never {
accept_init:
s0_init:
    if
    :: (r) -> goto s0_init
    :: !(s) -> goto s0_init
    :: !(p) && !(q) && !(r) && (s) -> goto accept_s1
    :: (q) -> goto s0_init
    fi;
accept_s1:
    if
    :: !(p) && !(q) && !(r) -> goto accept_s1
    :: (q) -> goto s0_init
    :: (r) -> goto s0_init
    fi;
}