import core.bitop, std.algorithm, std.ascii, std.bigint, std.conv, std.math,
    std.functional, std.numeric, std.range, std.stdio, std.string, std.random,
    std.typecons, std.container, std.format;

// dfmt off
T lread(T = long)(){return readln.chomp.to!T();}
T[] aryread(T = long)(){return readln.split.to!(T[])();}
void scan(TList...)(ref TList Args){auto line = readln.split();
foreach (i, T; TList){T val = line[i].to!(T);Args[i] = val;}}
alias sread = () => readln.chomp();enum MOD = 10 ^^ 9 + 7;
alias PQueue(T, alias less = "a<b") = BinaryHeap!(Array!T, less);
// dfmt on

void main()
{
    auto S = sread();
    long n = S.length;
    auto T = sread();
    {
        auto cnt = new long[]('z' - 'a' + 1);
        foreach (c; S)
            cnt[c - 'a']++;
        foreach (c; T)
            if (cnt[c - 'a'] == 0)
            {
                writeln(-1);
                return;
            }
    }
    auto next = new long[][](n, 'z' - 'a' + 1);
    auto SS = S ~ S;
    next[$ - 1][] = 0;
    next[$ - 1][S[0] - 'a'] = 1;
    foreach_reverse (i; 0 .. n * 2)
    {
        next[i % n][] = next[(i + 1) % n][] + 1;
        next[i % n][SS[i] - 'a'] = 0;
    }
    // foreach (i, r; next)
    //     writeln(i, " ", S[i], " ", r['t' - 'a']);
    // writeln();
    long cur = -1;
    foreach (c; T)
    {
        cur++;
        // writeln(cur, " ", c, " ", next[cur % n][c - 'a']);
        cur += next[cur % n][c - 'a'];
    }
    writeln(cur + 1);
}
