#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

int n,m;
char a[200005];
char b[5];

inline void in(int &n){
	n=0;
	char c=getchar();
	while(c<'0' || c>'9') c=getchar();
	while(c>='0'&&c<='9') n=n*10+c-'0',c=getchar();
	return ;
}

int main(){
	// freopen("flip.in","r",stdin);
	// freopen("flip.out","w",stdout);
	scanf("%s",a+1);
	scanf("%s",b+1);
	n=strlen(a+1),m=strlen(b+1);
	if(m==1){
		for(int i=1;i<=n;i++)
			if(a[i]==b[1]){puts("-1");return 0;}
		puts("0");
		return 0;
	}
	if(m<=2){
		int s1=0,s2=0;
		for(int i=1;i<=n;i++) s1+=(a[i]=='1'),s2+=(a[i]=='0');
		if(b[1]==b[2]){
			if(b[1]=='1'&&s1>s2+1){puts("-1");return 0;}
			if(b[1]=='0'&&s2>s1+1){puts("-1");return 0;}
		}
		int ans=0;
		for(int i=2;i<=n;i++)
			if(a[i-1]==b[1]&&a[i]==b[2]) ans++;
		printf("%d\n",ans);
		return 0;
	}
	if(b[1]==b[2]&&b[2]==b[3]){
		int ans=0;
		for(int i=1;i<=n;i++){
			if(a[i]!=b[1]) continue;
			int j=i;
			while(j<=n&&a[j]==a[i]) j++;
			j--;
			// printf("%d-%d\n",i,j);
			ans+=(j-i)/2;
			i=j;
		}
		printf("%d\n",ans);
		return 0;
	}
	int ans=0;
	for(int i=3;i<=n;i++)
		if(a[i-2]==b[1]&&a[i-1]==b[2]&&a[i]==b[3]) ans++;
	printf("%d\n",ans);
	return 0;

	return 0;
}