  We give an estimate for the width of the congruence subgroup
$\mathrm{SL}(n,O_S,I)$ in Tits--Vaserstein generators, where $O_S$ is a
localisation of the ring of integers in a number field $K$. We assume that
either $K$ has a real embedding, or the ideal $I$ is prime to the number of
roots of unity in $K$.
