#include <iostream>
#include <string>
using namespace std;
int a[128];
int main()
{
string s, t;
cin >> s >> t;
int posS = 0;
int posT = 0;
while (posT != t.size() && posS != s.size()){
if (s[posS] == t[posT]) {
++posS;
++posT;
} else {
++a[s[posS]];
++posS;
}
}
if (posT != t.size()) {
cout << "-1" << endl;
return 0;
}
for (int i = posS; i < s.size(); ++i)
a[s[i]]++;
int ans = 0;
for (auto &x : a)
{
ans = max(ans, (x + 1) / 2);
}
cout << ans << endl;
return 0;
}
