Suppose there are $n$ users each with public/private key pair $(pk\_i,sk\_i)$ $i=1,\cdots,n$. Is there any scheme that I can encrypt $m$ using the set of public keys $(pk\_1,\cdots,pk\_n)$, and can decrypt it using any $sk\_i$?
That is $C=Enc\_{(pk\_1,\cdots,pk\_n)}(m)$ and $m=Dec\_{any\ sk\_i}(C)$.

This is meaningful when these $n$ users are just a small portion of a group of $N$ users. A bit like "ring encryption" (opposite to ring signature). Thank you!