#include<bits/stdc++.h>
#define l size()-1
#define fo(i,l,r) for(int i=l;i<=r;i++)
#define fd(i,r,l) for(int i=r;i>=l;i--)
using namespace std;
int dp[27][10005];
int lpos,pos,ans=1;
string s1,s2;
map<char,bool>mp;
int main(){
	cin>>s1>>s2;
	fo(i,0,s1.l)mp[s1[i]]=1;
	fo(i,0,s2.l)
		if(!mp[s2[i]])return cout<<-1,0;
	fo(i,0,25)
		if(mp[i+'a']){
			int tmp=s1.l+1;
			fd(j,s1.l,0){
				if(s1[j]==i+'a')tmp=j;
				dp[i][j]=tmp;
			}
			fo(j,0,s1.l)
				if(dp[i][j]==s1.l+1)dp[i][j]=tmp;
		}
	fo(i,0,s2.l){
		if(s2[i]==s2[(i+s2.l)%s2.size()]){
			lpos=pos;
			pos=dp[s2[i]-'a'][(pos+1)%s1.size()]; 
		}
		else{
			lpos=pos;
			pos=dp[s2[i]-'a'][pos];
		}
		if(pos<=lpos)ans++;
	}
	cout<<ans;
	return 0;
}