#include <iostream>
#include <vector>
#include <cstdio>
#include <algorithm>
using namespace std;
 
#define maxn 300000
#define limit 1000000000000000000LL
 
long long k;
 
int n, m, i, j, cur, bad_value, kk;
char a[maxn], b[maxn];
bool was[30];
pair<int, int> srt[maxn * 2 + 3];
 
struct sfa {
 
	long long dp[maxn * 2 + 3], grundy_sum[30], ways[maxn * 2 + 3];
 
	int next[maxn * 2 + 3][26], len[maxn * 2 + 3], lnk[maxn * 2 + 3], grundy[maxn * 2 + 3];
	int nodes, last, j;
 
	void init () {
		nodes = last = 1;
		len[1] = lnk[1] = 0;
	}
 
	void push (int c) {
		int cur = ++nodes, p;
		len[cur] = len[last] + 1;
		for(p = last; p && !next[p][c]; p = lnk[p]) next[p][c] = cur;
		if (!p) lnk[cur] = 1; else {
			int q = next[p][c];
			if (len[p] + 1 == len[q]) lnk[cur] = q; else {
				int clone = ++nodes;
				len[clone] = len[p] + 1;
				for(int j = 0; j < 26; j++) next[clone][j] = next[q][j];
				lnk[clone] = lnk[q];
				for(; p && next[p][c] == q; p = lnk[p]) next[p][c] = clone;
				lnk[q] = lnk[cur] = clone;
			}
		}
		last = cur;
	}
 
	void grundy_precalc () {
		for(i = 1; i <= nodes; i++) srt[i] = make_pair(len[i], i);
		sort(srt + 1, srt + nodes + 1);
		for(i = 1; i <= nodes; i++) {
			int k = srt[nodes - i + 1].second;
			dp[k] = 1;
			for(j = 0; j < 30; j++) was[j] = 0;
			for(j = 0; j < 26; j++) if (next[k][j]) was[grundy[next[k][j]]] = true;
			for(j = 0; j < 30; j++) if (!was[j]) {
				grundy[k] = j;
				break;
			}
		}		
	}	
 
	void substr_precalc () {
		for(i = 1; i <= nodes; i++) srt[i] = make_pair(len[i], i);
		sort(srt + 1, srt + nodes + 1);
		for(i = 1; i <= nodes; i++) {
			int k = srt[nodes - i + 1].second;
			dp[k] = 1;
			for(j = 0; j < 26; j++) if (next[k][j]) dp[k] += dp[next[k][j]];
		}
		ways[1] = 1;
		for(i = 1; i <= nodes; i++) for(j = 0; j < 26; j++) if (next[srt[i].second][j]) ways[next[srt[i].second][j]] += ways[srt[i].second];
		for(i = 1; i <= nodes; i++) grundy_sum[grundy[i]] += ways[i];
	}
 
	void dp_recalc (int bad_value) {
		for(i = 1; i <= nodes; i++) srt[i] = make_pair(len[i], i);
		sort(srt + 1, srt + nodes + 1);
		for(i = 1; i <= nodes; i++) {
			int k = srt[nodes - i + 1].second;
			dp[k] = grundy[k] != bad_value;
			for(j = 0; j < 26; j++) if (next[k][j]) dp[k] += dp[next[k][j]];
		}
	}
 
} sfa1, sfa2;
 
int main (int argc, char * const argv[]) {
//	freopen("input.txt", "r", stdin);
	scanf("%d %d %lld\n", &n, &m, &k);
 
	sfa1.init();
	sfa2.init();
 
	for(i = 0; i < n; i++) {
		a[i] = getchar();
		while (a[i] < 'a' || a[i] > 'z') a[i] = getchar();
		sfa1.push(a[i] - 'a');
	}
	for(i = 0; i < m; i++) {
		b[i] = getchar();
		while (b[i] < 'a' || b[i] > 'z') b[i] = getchar();
		sfa2.push(b[i] - 'a');
	}
 
	sfa1.grundy_precalc();
	for(i = 1; i <= sfa2.nodes; i++) was[i] = false;
	sfa2.grundy_precalc();
 
	sfa2.substr_precalc();	
 
	for(i = 1; i <= sfa1.nodes; i++) srt[i] = make_pair(sfa1.len[i], i);
	sort(srt + 1, srt + sfa1.nodes + 1);
	for(i = 1; i <= sfa1.nodes; i++) {
		kk = srt[sfa1.nodes - i + 1].second;
		sfa1.dp[kk] = sfa2.dp[1] - sfa2.grundy_sum[sfa1.grundy[kk]];
		for(j = 0; j < 26; j++) if (sfa1.next[kk][j]) {
			sfa1.dp[kk] += sfa1.dp[sfa1.next[kk][j]];
			if (sfa1.dp[kk] > limit) sfa1.dp[kk] = limit;
		}
	}		
 
	if (k > sfa1.dp[1]) {
		puts("no solution");
		return 0;
	}
 
	cur = 1;
	while (k > 0) {
		if (k <= sfa2.dp[1] - sfa2.grundy_sum[sfa1.grundy[cur]]) break; else k -= sfa2.dp[1] - sfa2.grundy_sum[sfa1.grundy[cur]];
		for(j = 0; j < 26; j++) if (k > sfa1.dp[sfa1.next[cur][j]]) k -= sfa1.dp[sfa1.next[cur][j]]; else {
			putchar('a' + j);
			cur = sfa1.next[cur][j];
			break;
		}
	}
	puts("");	
 
	sfa2.dp_recalc(bad_value = sfa1.grundy[cur]);
	cur = 1;
	while (k > 0) {
		if (sfa2.grundy[cur] != bad_value) {
			--k;
			if (k == 0) break;
		}
		for(j = 0; j < 26; j++) if (k > sfa2.dp[sfa2.next[cur][j]]) k -= sfa2.dp[sfa2.next[cur][j]]; else {
			putchar('a' + j);
			cur = sfa2.next[cur][j];
			break;
		}
	}
	puts("");
    return 0;
}