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B.cpp
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B.cpp
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#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define lb lower_bound
#define ub upper_bound
#define ff first
#define ss second
#define rep(i, a, b) for(int i = a; i < b; i++)
#define repR(i, a, b) for (int i = a; i >= b; --i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) (int)(x).size()
#define mem1(a) memset(a,-1,sizeof(a))
#define mem0(a) memset(a,0,sizeof(a))
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define vi vector<int>
#define vvi vector<vi>
#define vll vector<ll>
#define vvll vector<vll>
#define vs vector<string>
#define vb vector<bool>
#define vpii vector<pii>
#define vpll vector<pll>
#define mod 1000000007
#define ps(x,y) fixed << setprecision(y) << x
#define fastio ios_base::sync_with_stdio(false),cin.tie(NULL),cout.tie(NULL)
set<char> p = {'1', '4', '6', '8', '9'};
bool check(int n)
{
for (int i = 2; i * i <= n; i++) {
if (n % i == 0) return false;
}
return true;
}
void solve()
{
int n;
string s;
cin >> n >> s;
map<int, int> cnt;
rep(i, 0, n) {
cnt[s[i] - '0']++;
if (p.count(s[i])) {
cout << 1 << '\n';
cout << s[i] << '\n';
return;
}
}
for (auto it : cnt) {
if (it.ss >= 2) {
cout << 2 << '\n';
cout << it.ff << it.ff << '\n';
return;
}
}
rep(i, 0, n) {
rep(j, i + 1, n) {
int num = ((s[i] - '0') * 10) + (s[j] - '0');
if (!check(num)) {
cout << 2 << '\n';
cout << num << '\n';
return;
}
}
}
cout << n << '\n';
cout << s << '\n';
}
int main()
{
fastio;
/*#ifndef ONLINE_JUDGE
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
#endif*/
int t = 1;
cin >> t;
while (t--) solve();
return 0;
}