package main
import (
"regexp"
"fmt"
)
func main() {
var re = regexp.MustCompile(`\b1([a-z])(?=[^#]*#[^#]*(?:[^#]*#[^#]*#[^#]*)*$)`)
var str = `As a 1st step, you can rewrite #21x*x - 1y = 1z + 1#. But what about the 2nd #3x + 1y = 1z#?`
var substitution = "$1"
fmt.Println(re.ReplaceAllString(str, substitution))
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Golang, please visit: https://golang.org/pkg/regexp/