#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,a,b,c;
    cin>>n;
    a=n*0.1;
    b=n-10*a;
    c=10*b+a;
    if(a>c)
        cout<<a;
    else
        cout<<c;
    return 0；
}

已AC

#include <bits/stdc++.h>
using namespace std;
int n;
int main()
{
    cin >> n;
    cout << max(n, n % 10 * 10 + n / 10);
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int x;
    cin>>x;
    cout<<max(x,x%10*10+x/10);
    return 0;
}

#include <iostream>
using namespace std;
int main()
{
    int n;
    cin >> n;
    if(n%10>=n/10)
    {
        cout << n%10 << n/10;
    }
    else
    {
        cout << n/10 << n%10;
    }
}