uva1392

#include <iostream>
#include <istream>
#include <sstream>
#include <vector>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <numeric>
#include <chrono>
#include <ctime>
#include <cmath>
#include <cctype>
#include <string>
#include <cstdio>
#include <iomanip>


#include <thread>
#include <mutex>
#include <condition_variable>
#include <functional>
#include <iterator>
using namespace std;
const int maxn = 2e5 + 7;
int cnt[maxn] = { 0 }, nmax[maxn] = {0}, sum[maxn] = { 0 }, n, p;
char a[maxn], b[maxn];

bool ok(long long int mid) {
	for (int i = mid; i <= n; i++) {
		if (sum[i] <= nmax[i - mid]) return true;
	}
	return false;
}
int main() {
	while (cin >> n >> p && n && p) {
		cin >> a >> b;
		for (int i = 0; i < n; i++) {
			cnt[i + 1] = cnt[i] + (a[i] != b[i]);
		}
		for (int i = 1; i <= n; i++) sum[i] = 100 * cnt[i] - p * i;
		for (int i = 1; i <= n; i++) nmax[i] = max(nmax[i - 1], sum[i]);
		int l = 0, r = n;
		while (l < r) {
			int mid = (l + r + 1) >> 1;
			if (ok(mid)) {
				l = mid;
			}
			else r = mid - 1;
		}
		if (!l) cout << "No solution." << endl;
		else cout << l << endl;
	}
	return 0;
}