375A - Divisible by Seven - CodeForces Solution

/*
*   -------------- ?*?*? --------------
* |         In The Name of *Allah*     |
* |             Author : Tarik         |
* |                                    |
*  -------------- ?*?*? ---------------
*/
 
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
#define  fastio    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
#define  int       long long
#define  pb        push_back
#define  all(v)    v.begin(),v.end()
#define  endl       '\n'   
typedef tree<int,null_type,less_equal<int>,rb_tree_tag,tree_order_statistics_node_update>ordered_set; 
 
const int mxn=1e6+123;
int a[mxn];
void solve(){

	string s;cin>>s;
	sort(s.begin(),s.end());
	int cnt=0;
	for(auto x:s){
		if(x=='0')cnt++;
		else break;
	}
	reverse(s.begin(),s.end());
	while(1){
		random_shuffle(s.begin(),s.end()-cnt);
		int sum=0;
		for(int i=0;i<s.size()-cnt;i++){
			sum=sum*10+(s[i]-'0');
			sum%=7;
		}
		if(sum==0){
			cout<<s<<endl;
			return;
		}
	}
	
}
signed main(){ 
    fastio; 
    int t=1;
    //cin>>t;
    while(t--){
       solve();
    }
}