codeforce - Nirvana

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fastread()(ios_base:: sync_with_stdio(false),cin.tie(NULL));
int main()
{
    fastread();
    ll n,res;
    cin>>n;
    res=n/10;
    res=res*10-1;
    //cout<<n<<" "<<res<<endl;
    ll x=1,y=1,mx,sub=res;
    while(n>0)
    {
        x*=(n%10);
        n/=10;
    }
    while(res>0)
    {
        y*=(res%10);
        res/=10;
    }
    mx=max(x,y);
    ll i=100;
    while(sub>i)
    {
        res=sub/i;
        res=res*i-1;
        y=1;
        while(res>0)
        {
            y*=(res%10);
            res/=10;
        }
        mx=max(mx,y);
        i*=10;
    }
    cout<<mx<<endl;
    return 0;
}