Champernowne‘s constant

#include<bits/stdc++.h>
using namespace std;

#define rep(i,l,r) for(int i=(l);i<=(r);i++)
#define per(i,l,r) for(int i=(l);i>=(r);i--)
#define ll long long
#define mset(s,t) memset(s,t,sizeof(t))
#define mcpy(s,t) memcpy(s,t,sizeof(t))
#define fi first
#define se second
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())
#define mp make_pair

typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;   
typedef vector<ll> Vll;               
typedef vector<pair<int, int> > vpii;
typedef vector<pair<ll, ll> > vpll;                        

const ll mod = 1e9 + 7;
//const ll mod = 998244353;
const double pi  = acos(-1.0);

inline ll qmi (ll a, ll b) {
    ll ans = 1;
    while (b) {
        if (b & 1) ans = ans * a%mod;
        a = a * a %mod;
        b >>= 1;
    }
    return ans;
}
inline int read () {
    int x = 0, f = 0;
    char ch = getchar();
    while (!isdigit(ch)) f |= (ch=='-'),ch= getchar();
    while (isdigit(ch)) x = x * 10 + ch - '0', ch = getchar();
    return f?-x:x;
}
template<typename T> void print(T x) {
    if (x < 0) putchar('-'), x = -x;
    if (x >= 10) print(x/10);
    putchar(x % 10 + '0');
}
inline ll sub (ll a, ll b) {
    return ((a - b ) %mod + mod) %mod;
}
inline ll add (ll a, ll b) {
    return (a + b) %mod;
}
inline ll inv (ll a) {
    return qmi(a, mod - 2);
}
const int N = 1e6 + 10;

int get (int n) {
    
    if (n < 10) return n;
    int start = 1, dig =1;
    int count = 9;
    
    
    while (n > count) {
        n -= count;
        dig += 1;
        start *= 10;
        count = start * 9 * dig;
    }
    string num = to_string(start + (n) / dig);
    return num[n % dig] - '0';
}
 int get1(int n) {
        // write code here int r = n %10;
      long long count = 9, dig = 1;
       long long start = 1;
        if (n < 10) return n; 
        while (n > count) {
            n -= count;
            dig += 1;
            start *= 10;
            count = start * 9 * dig;
        }
        string num = to_string(start + (n - 1) / dig);
        return num[(n - 1) % dig] - '0';
    }
void solve() {
    int start = 1;
    int ans = 1;
    cout << get1(15) << endl;
    for (int i =1; i <= 1000000; i *= 10) {
        ans *= get1(i);
    }
    print(ans);
}
int main () {
    // ios::sync_with_stdio(0),cin.tie(0), cout.tie(0);
    int t;
    t =1;
    //cin >> t;
    while (t --) solve();
    return 0;
}

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