import java.util.*

fun main(args: Array<String>) = IO().exec {
    val s = string()
    val t = string()
    val indices = GenIntArray2d(26).build {
        for (i in s.length) push(s[i] - 'a', i)
        for (i in s.length) push(s[i] - 'a', i + s.length)
    }

    var p = 0
    var lencnt = 0L
    for (c in t) {
        val j = lowerBound(indices[c-'a'], p)
        if (j == indices[c-'a'].size) {
            println(-1)
            return@exec
        }
        p = indices[c-'a'][j] + 1
        if (p >= s.length) {
            p -= s.length
            lencnt++
        }
    }
    println(p + lencnt * s.length)
}

fun lowerBound(arr: IntArray, x: Int): Int {
    var ok = arr.size
    var ng = -1
    while (Math.abs(ok - ng) > 1) {
        val mid = (ok + ng) / 2
        if (arr[mid] >= x) {
            ok = mid
        } else {
            ng = mid
        }
    }
    return ok
}

class GenIntArray2d(val n: Int) {
    lateinit var ret: Array<IntArray>
    var isInit = true
    var cnt = IntArray(n)
    fun push(i: Int, item: Int) {
        if (isInit) cnt[i]++ else ret[i][cnt[i]++] = item
    }
    inline fun build(fn: GenIntArray2d.() -> Unit): Array<IntArray> {
        fn()
        isInit = false
        ret = Array(n){IntArray(cnt[it])}
        cnt = IntArray(n)
        fn()
        return ret
    }
}

// region template
operator fun Int.iterator() = 0.until(this).iterator()

class IO {
    val printable = 33..126
    val buffer = ByteArray(1024)
    var ptr = 0
    var buflen = 0
    val out = java.io.PrintWriter(System.out)
    fun hasNextByte(): Boolean = if (ptr < buflen) true else {
        ptr = 0
        buflen = System.`in`.read(buffer)
        buflen > 0
    }

    fun readByte(): Byte = if (hasNextByte()) buffer[ptr++] else -1
    fun hasNext(): Boolean {
        while (hasNextByte() && buffer[ptr] !in printable) ptr++
        return hasNextByte()
    }

    fun string(): String {
        if (!hasNext()) throw java.util.NoSuchElementException()
        val sb = StringBuilder()
        var b = readByte()
        while (b in printable) {
            sb.appendCodePoint(b.toInt())
            b = readByte()
        }
        return sb.toString()
    }

    fun long(): Long {
        if (!hasNext()) throw java.util.NoSuchElementException()
        var n = 0L
        var minus = false
        var b = readByte()
        if (b == '-'.toByte()) {
            minus = true
            b = readByte()
        }
        if (b !in '0'.toByte()..'9'.toByte()) {
            throw NumberFormatException()
        }
        while (true) {
            if (b in '0'.toByte()..'9'.toByte()) {
                n *= 10
                n += b - '0'.toByte()
            } else if (b == (-1).toByte() || b !in printable) {
                return if (minus) -n else n
            } else {
                throw NumberFormatException()
            }
            b = readByte()
        }
    }

    fun int(): Int {
        val nl = long()
        if (nl !in Integer.MIN_VALUE..Integer.MAX_VALUE) throw NumberFormatException()
        return nl.toInt()
    }

    fun double(): Double = string().toDouble()
    fun print(obj: Any) = out.print(obj)
    fun print(i: Int) = out.print(i)
    fun print(l: Long) = out.print(l)
    fun println(obj: Any) = out.println(obj)
    fun println(i: Int) = out.println(i)
    fun println(l: Long) = out.println(l)
    inline fun exec(block: IO.() -> Unit) {
        block()
        out.flush()
    }
}
// endregion

Measured memory_bytes: 33436