Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	io := NewIo()
	defer io.Flush()
	q := io.NextInt()
	for i := 0; i < q; i++ {
		io.Println(solve(io.NextInt()))
	}
}

func solve(n int) int {
	f := func(n int) int {
		max := 0
		for i := 10; ; i *= 10 {
			a := n / i
			b := n % i
			if a == 0 {
				break
			}
			max = intMax(a*b, max)
		}
		return max
	}

	cnt := 0
	for {
		if n < 10 {
			break
		}
		n = f(n)
		cnt++
	}

	return cnt
}

func intMax(a, b int) int {
	if a < b {
		return b
	}
	return a
}

// I/O template
type Io struct {
	reader    *bufio.Reader
	writer    *bufio.Writer
	tokens    []string
	nextToken int
}

func NewIo() *Io {
	return &Io{
		reader: bufio.NewReader(os.Stdin),
		writer: bufio.NewWriter(os.Stdout),
	}
}

func (io *Io) Flush() {
	err := io.writer.Flush()
	if err != nil {
		panic(err)
	}
}

func (io *Io) NextLine() string {
	var buff []byte
	for {
		line, isPrefix, err := io.reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buff = append(buff, line...)
		if !isPrefix {
			break
		}
	}
	return string(buff)
}

func (io *Io) Next() string {
	for io.nextToken >= len(io.tokens) {
		line := io.NextLine()
		io.tokens = strings.Fields(line)
		io.nextToken = 0
	}
	s := io.tokens[io.nextToken]
	io.nextToken++
	return s
}

func (io *Io) NextInt() int {
	i, err := strconv.Atoi(io.Next())
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) NextFloat() float64 {
	i, err := strconv.ParseFloat(io.Next(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) Println(a ...interface{}) {
	fmt.Fprintln(io.writer, a...)
}

func (io *Io) Printf(format string, a ...interface{}) {
	fmt.Fprintf(io.writer, format, a...)
}

func (io *Io) PrintIntSlice(a []int) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func (io *Io) PrintStringSlice(a []string) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func Log(name string, value interface{}) {
	fmt.Fprintf(os.Stderr, "%s=%+v\n", name, value)
}

func ExampleIo() {
	io := NewIo()
	defer io.Flush()
	a := make([]int, 0, 3)
	a[0], a[1], a[2] = io.NextInt(), io.NextInt(), io.NextInt()
	io.Println(a)
	io.PrintIntSlice(a)
	Log("io", a)
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <stack>
#include <cstring>
#include <string>
#include <queue>
#include <cmath>
#include <map>

#define rep(i,n) for(int i = 0; i < (n); i++)
#define all(v) (v).begin(), (v).end()
#define rev(v) (v).rbegin(), (v).rend()
#define MP make_pair
#define X first
#define Y second

using namespace std;

typedef vector<int> vi;
typedef pair<int, int> P;
typedef long long ll;


bool visit[1000001];

int check(int n, int cnt = 0){
	if(cnt == 0){
		memset(visit, false, sizeof(visit));
	}
	if(n < 10) return cnt;
	if(visit[n]) return -1;
	visit[n] = 1;

	int	next = 0;
	int k, m = n;
	for(int i = 10; m > 0; i*=10){
		k = n%i;
		m = n/i;
		next = max(next, k*m);
	}
	return check(next, cnt+1);
}

int main(){
	int Q;
	cin >> Q;
	while(Q--){
		int n;
		cin >> n;
		cout << check(n) << endl;
	}


	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <stack>
#include <queue>
//ranker
using namespace std;

#define REPS(i, a, n) for (int i = (a); i < (n); ++i)
#define REP(i, n) REPS(i, 0, n)
#define RREP(i, n) REPS(i, 1, n + 1)
#define DEPS(i, a, n) for (int i = (a); i >= n; --i)
#define DEP(i, n) DEPS(i, n, 0)

using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using pii = pair<int, int>;
using pis = pair<int, string>;
using psi = pair<string, int>;
using D = double;

void merge (int *first1, int *last1, int *first2, int *last2){
    int size1 = last1 - first1;
    int size2 = last2 - first2;
    int *result = new int[size1+size2];
    int i = 0;
    int j = 0;
    int index = 0;
    while (true){
        if (i < size1 && (first1[i] <= first2[j] || j >= size2)){
            result[index] = first1[i];
            ++i; ++index;
        }
        if (j < size2 && (first1[i] > first2[j] || i >= size1)){
            result[index] = first2[j];
            ++j; ++index;
        }
        if (i==size1 && j==size2){
            for (i=0; i<size1; ++i) first1[i] = result[i];
            for (j=0; j<size2; ++j) first2[j] = result[j+size1];
            delete[] result;
            return;
        }
    }
}
void MergeSort (int *first, int *last){
    int size = last - first;
    if(size <= 1) return;
    MergeSort(first, first+size/2);
    MergeSort(first+size/2, last);
    merge(first, first+size/2, first+size/2, last);
}

//?????°????????????
void sort2vectors(vector<int> &av, vector<int> &bv)
{
        int n = av.size();
        vector<int> p(n), av2(n), bv2(n);
        iota(p.begin(), p.end(), 0);
        sort(p.begin(), p.end(), [&](int a, int b) { return av[a] < av[b]; });
        for (int i = 0; i < n; i++) {
                av2[i] = av[p[i]];
                bv2[i] = bv[p[i]];
        }
        av = av2;
        bv = bv2;
}


int gcd(int a, int b)
{
    int c;
    if (a < b) {
        a+=b; b=a-b; a-=b;
    }
    while (b != 0) {
        c = a % b;
        a = b;
        b = c;
    }
    return a;
}

int isPrime(int x){
  int i;
  if(x < 2) return 0;
  else if(x == 2) return 1;
  if( x%2 == 0) return 0;
  for(i = 3; i*i <= 2; i += 2){
    if(x%i == 0) return 0;
  }
  return 1;
}


const int pmax = 10000000;
bool isPrime_table[pmax];
//const???????????¨????????£?¨???§?????????

void eratos(void){
  int i, j;
  double sqrtmax=sqrt(pmax);

  REP(k, pmax) isPrime_table[k] = true; /* Initialization */

  /* Sieve process  */
  isPrime_table[0] = false;
  isPrime_table[1] = false;
          /* 0 and 1 are not prime. */
  for (i=2; i <= sqrtmax; i++){
    if (isPrime_table[i]==true){   /* i is prime. */
      for (j=i; i*j<pmax; j++){
        isPrime_table[i*j] = false; /* multiples of i are not prime. */
      }
    }
  }
}

//????????????????¨???°?????????
//abs(dx[i]+dy[j])==1??§??????
int dx[3]={-1, 0, 1};
int dy[3]={-1, 0, 1};
int W0, H0;
int  masu0[100][100]={0};
int cnt0;

int dfs(int a, int b){
  masu0[a][b] = 2;
  REP(i, 3)REP(j, 3){
    a = a+dx[i];
    b = b+dy[j];
    if(masu0[a][b]== 1 && a >= 0 && a < W0 && b >= 0 && b < H0){
    dfs(a, b);
  }
  }
  return 1;
}

//????????????????????????str.substr(i, 5)
//????????°????????? stoi, stod ??¨to_string
//?????????memset
//?????°??????????????????
//dp

int main(void){
  cin.tie(0);
  ios::sync_with_stdio(false);

    int Q;
    cin >> Q;

    for(int i = 0; i<Q; i++){
        string suji;
        cin >> suji;

        int len = suji.length();
        int cnt = 0;
        while(stoi(suji) >= 10){
          int max = -1;
        for(int j = 1; j<suji.length(); j++){
            int num1;
            int num2;
            int tot;
            num1 = stoi(suji.substr(0, j));
            num2 = stoi(suji.substr(j, suji.length()-j));
            tot = num1*num2;
            if(max < tot) max = tot;
        }
        cnt++;
        suji = std::to_string(max);
      }
        cout << cnt << endl;
    }
    return 0;
}