#include<iostream>
#include<cstdio>
#include<algorithm>
#include<memory.h>
#include<vector>
#include<stack>
#include<queue>
#include<cassert>
#include<cstdlib>
#include<cmath>
#include<map>
#include<cstring>
#define debug(x) cout<<#x<<"= "<<x<<endl
#define mod(x) ((x)>0)?(x):(-(x))
#define MAX(a,b) ((a)>(b))? (a):(b)
#define MIN(a,b) ((a)<(b))? (a):(b)
#define bit(n,i) (n&(1<<(i-1)))
#define setbit(n,i) n |= (1<<(i-1))
#define inf (1<<30)
#define SETZERO(x) memset( x, 0, sizeof(x))
#define SETMIN1(x) memset( x, -1, sizeof(x))
#define CLEAR(x) while(!x.empty()) x.pop();
using namespace std;
char a[1001],b[1001];
int sa,sb;
long long mf[1001][1001];
long long MAXRET = (1ll<<31);
long long f( int i, int j)
{
if( i == sa || j == sb)
return 1;
long long &ret = mf[i][j];
if( ret >= 0)
return ret;
if( a[i] == b[j])
{
ret=f( i+1, j+1);
}
else
{
ret=f( i, j+1)+f( i+1, j);
}
if(ret>MAXRET) ret = MAXRET*2;
return ret;
}
void output( long long n, int i, int j)
{
if( i == sa && j == sb)
return;
if( i == sa)
printf("%s", &b[j]);
else
if( j == sb)
printf("%s", &a[i]);
else
if( a[i] == b[j])
printf( "%c", a[i]),output( n, i+1, j+1);
else
if(a[i]<b[j]){
if( f( i+1, j) >= n)
printf( "%c", a[i]),output( n, i+1, j);
else
printf( "%c", b[j]),output( n-f(i+1,j), i, j+1);
}
else{
if( f( i, j+1) >= n)
printf( "%c", b[j]),output( n, i, j+1);
else
printf( "%c", a[i]),output( n-f(i,j+1), i+1, j);
}
}
int main()
{
#ifndef ONLINE_JUDGE
freopen( "a.in", "r", stdin);
freopen( "a.out", "w", stdout);
#endif
int t;
scanf("%d",&t);
while(t--)
{
SETMIN1( mf);
long long n;
scanf( "%s\n%s", a, b);
sa = strlen(a);
sb = strlen(b);
cin >> n;
if( f(0,0) < n)
{
cout<<"NO ANSWER";
}
else
{
output( n, 0, 0);
}
cout<<"\n";
}
}
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