#include <fstream>
#include <vector>

using namespace std;

int main() {
    string t, s;

    ifstream inp("input.txt");

    getline(inp, s);
    getline(inp, t);

    inp.close();

    int n = t.size();
    vector<int> pi (n);
    for (int i = 1; i < n; ++i) {
        int k = pi[i - 1];
        while (k > 0 && t[i] != t[k])
            k = pi[k - 1];
        if (t[i] == t[k])
            ++k;
        pi[i] = k;
    }
    //bool onechar = false;
    //if (t.size() == 1)
    //    onechar = true;
    int pos = -1, q = 0;
    for (int i = 0; i < s.size(); ++i) {
        //if (onechar) {
        //    if (t[0] == s[i]) {
        //        ofstream out("output.txt");
        //        out << i + 1;
        //        out.close();
        //        return 0;
        //    }
        //}
        while (q > 0 && t[q] != s[i]) {
            q = pi[q-1];
        }
        if (t[q] == s[i]) {
            q++;
        }
        if(q == t.size()) {
            pos = i - q + 2;
            break;
        }
    }


    ofstream out("output.txt");
    //if (onechar) {
    //    out << "-1";
    //}
    //else {
        out << pos;
    //}
    out.close();
    return 0;
}