1function hash1(s) { let h = 0; for (c of s) h = (h*31 + c) % m; return h; }
2function hash2(s) { let h = 7; for (c of s) h = (h*17 + c) % m; return h; }
3function hash3(s) { let h = 0; for (c of s) h = (h*131 + c) % m; return h; }
4function add(s) { bits[hash1(s)]=bits[hash2(s)]=bits[hash3(s)]=1; }
5function has(s) { return bits[hash1(s)] && bits[hash2(s)] && bits[hash3(s)]; }