Problem #40

Problem link
Solution:

package main

import (
    "strconv"
)

func main() {
    i, count, limit, mul := 1, 0, 10, 1
    var tmp int
    for limit < 1000001 {
        str := strconv.Itoa(i)
        count += len(str)
        if count >= limit {
            tmp, _ = strconv.Atoi(str[len(str)-(count-limit)-1 : len(str)-(count-limit)])
            mul *= tmp
            limit *= 10
        }
        i++
    }
    println(mul)
}

Result: 210
Time: 0m0.153s