#include<cstdio>
#include<algorithm>
using namespace std;
int main()
{
char a[1000000];
int t,n,i;
scanf("%d ",&t);
while(t-->0)
{
scanf("%d",&n);
for(i=0;i<n;i++)
{
scanf(" %c",&a[i]);
}
//for(i=0;i<n;i++)
// printf("%c",a[i]);
// printf("\n");
if(n==1)
printf("-1\n");
else
{
for(i=n-2;i>=0;i--)
{
if(a[i]<a[i+1])
break;
}
}
if(i<0)
printf("-1\n");
else
{
//printf("%d\n",i);
char temp=a[i];
for(int j=n-1;j>i;j--)//finding highest index j such that a[j]>a[i]
{
if(a[i]<a[j])
{
//printf("%d\n",j);
a[i]=a[j];
a[j]=temp; //swapping a[j] & a[i]
// printf("%c%c\n",a[i],a[j]);
}
}
}
//for(i=0;i<n;i++) this step was giving run time error
//printf("%c",a[i]);
printf("\n");
sort(a+i+1,a+n);
for(int j=0;j<n;j++)printf("%d",a[j]);
printf("\n");
}
return 0;
}
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