void Helper(vector<int> v, int low, int high){    if(low == high)    {        for(int i = 0; i < v.size(); i ++)            cout << v[i];        cout << endl;    }    else    {        for(int i = low; i <= high; i ++)        {            swap(v[low], v[i]);            Helper(v, low+1, high);            swap(v[low], v[i]);        }    }}void permutation(int n){    vector<int> v(n,0);    for(int i = 0; i < n; i ++)        v[i] = i+1;    Helper(v, 0, n-1);}

void permutation(int n){    vector<int> v(n,0);    for(int i = 0; i < n; i ++)        v[i] = i+1;    do    {        for(int i = 0; i < v.size(); i ++)            cout << v[i];        cout << endl;    }while(next_permutation(v.begin(),v.end()));}