F

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

int main(){
    string s,o;
    pair<long long, long long> currentmin(INT_MAX, -1);
    cin>>s;
    int n=s.length(),i,j;
    o=s;
    for(i=n-2; i>=0; i--){
        bool change=0;
        for(j=i+1; j<n; j++){
            if(s[i]<s[j] && currentmin.first>s[j]){
                currentmin.first = s[j];
                currentmin.second = j;
                change=1;
            }
        }
        if(change){
            swap(s[i],s[currentmin.second]);
            sort(s.begin()+i+1, s.end());
            break;
        }

    }
    if(s.compare(o)!=1)cout<<0<<endl;
    else cout<<s<<endl;

return 0;
}