from heapq import heappush,heappop
from collections import deque
t = 1
for tc in range(1,t+1):
s = input()
p = input()
cols = {}
for c in s:
if c not in cols:
cols[c]=[0,0]
cols[c][0]+=1
ans = 0
for c in p:
if c not in cols:
ans=-1
break
cols[c][1]+=1
if ans==-1:
print(ans)
continue
for c in cols:
ans+=min(cols[c])
print(ans)#include<bits/stdc++.h>
using namespace std;
#define fast() ios_base::sync_with_stdio(false); cin.tie(NULL);
#define ll long long int
#define ull unsigned long long int
#define nl "\n"
#define MOD 1000000009
#define pb push_back
#define ppb pop_back
#define dbg(x) cerr<<#x<<"-"<<x<<nl;
#define siz 100005
// solve function
void solve(){
string a,b;
cin>>a>>b;
vector<ll>x(26,0);
vector<ll>y(26,0);
for(int i=0;i<(int)a.length();i++) ++x[a[i]-'a'];
for(int j=0;j<(int)b.length();j++) ++y[b[j]-'a'];
ll res = 0;
for(int i=0;i<26;i++){
if(x[i]==0 && y[i]!=0){
cout<<-1<<nl;
return;
}
res += min(x[i],y[i]);
}
cout<<res<<nl;
}
/* main function */
int main(){
clock_t start,end;
start=clock();
fast();
ll t=1;
ll i=1;
/* cin>>t; */
while(t--){
/* cout<<"Case# "<<i<<": "; */
solve();
i++;
}
end=clock();
double time=double(end-start)/double(CLOCKS_PER_SEC);
cerr<<nl<<"Time: "<<time<<" sec"<<nl;
}
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