#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e6 + 5;
int n, m, nxt[maxn];
char s[maxn], t[maxn];

void cal_nxt() { 
	nxt[1] = 0;
	for (int i = 2, j = 0; i <= m; i++) {
		while (j && t[j+1] != t[i])
			j = nxt[j];
		if (t[j+1] == t[i]) j++;
		nxt[i] = j;
	}
}

void kmp() {
	for (int i = 1, j = 0; i <= n; i++) {
		while (j && t[j+1] != s[i])
			j = nxt[j];
		if (t[j+1] == s[i]) {
			j++;
			if (j == m) {
				printf("%d\n", i - m + 1);
				return;
			}
		}
	}
	puts("-1");
}

int main() {
	scanf("%s%s", s+1, t+1);
	n = strlen(s+1);
	m = strlen(t+1);
	cal_nxt();
	kmp();
	return 0;
}