return i
			}
			fails++
			i++
			// Switch to bytealg.Index when IndexByte produces too many false positives.
			if fails > bytealg.Cutover(i) {
				r := bytealg.Index(s[i:], sep)
				if r >= 0 {
					return r + i
				}
				return -1
			}
		}
		return -1
	}
	c0 := sep[0]
	c1 := sep[1]
	i := 0
	fails := 0
	t := len(s) - n + 1
	for i < t {