import java.io.*;
import java.util.InputMismatchException;

class Main {
    public static void main(String[] args) throws IOException {
        OutputStream out = new BufferedOutputStream(System.out);
        Scan scan = new Scan();
        String s = scan.scanString();
        String t = scan.scanString();
        if (s.equals(t.substring(0,s.length())) && s.length()+1==t.length()){
            out.write(("Yes"+"\n").getBytes());
        }else{
            out.write(("No"+"\n").getBytes());
        }
        out.flush();
    }
    private static class FastReader{
        final private int BUFFER_SIZE = 1 << 16;
        private byte[] buffer;
        private DataInputStream din;
        private int bufferPointer, bytesRead;

        public FastReader(){
            buffer = new byte[BUFFER_SIZE];
            din = new DataInputStream(System.in);
            bufferPointer = bytesRead = 0;
        }

        private String nextLine() throws IOException {
            StringBuilder sb = new StringBuilder();
            byte c;
            while((c = read()) != -1 && c != '\n'){
                sb.appendCodePoint(c);
            }
            return sb.toString();
        }

        private int nextInt() throws IOException{
            int ret = 0;
            byte c = read();
            while(c <= ' '){
                c = read();
            }
            boolean neg = c == '-';
            if(neg){
                c = read();
            }
            while(c >= '0' && c <= '9'){
                ret = ret * 10 + c - '0';
                c = read();
            }
            return (neg) ? -ret : ret;
        }

        private long nextLong() throws IOException{
            long ret = 0;
            byte c = read();
            while(c <= ' '){
                c = read();
            }
            boolean neg = c == '-';
            if(neg){
                c = read();
            }
            while(c >= '0' && c <= '9'){
                ret = ret * 10 + c - '0';
                c = read();
            }
            return (neg) ? -ret : ret;
        }

        private double nextDouble() throws IOException{
            double ret = 0, div = 1;
            byte c = read();
            while(c <= ' '){
                c = read();
            }
            boolean neg = c == '-';
            if(neg){
                c = read();
            }
            while(c >= '0' && c <= '9'){
                ret = ret * 10 + (c - '0');
                c = read();
            }
            if(c == '.'){
                while((c = read()) >= '0' && c <= '9'){
                    ret += (c - '0') / (div *= 10);
                }
            }
            return (neg) ? -ret : ret;
        }

        private void fillBuffer() throws IOException {
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
            if(bytesRead == -1){
                buffer[0] = -1;
            }
        }

        private byte read() throws IOException {
            if(bufferPointer == bytesRead){
                fillBuffer();
            }
            return buffer[bufferPointer++];
        }

        private void close() throws IOException{
            if(din != null){
                din.close();
            }
        }

    }

    private static class Scan{
        private byte[] buf=new byte[1024];
        private int index;
        private InputStream in;
        private int total;
        public Scan()
        {
            in=System.in;
        }
        public int scan()throws IOException
        {
            if(total<0)
                throw new InputMismatchException();
            if(index>=total)
            {
                index=0;
                total=in.read(buf);
                if(total<=0)
                    return -1;
            }
            return buf[index++];
        }
        public int scanInt()throws IOException
        {
            int integer=0;
            int n=scan();
            while(isWhiteSpace(n))
                n=scan();
            int neg=1;
            if(n=='-')
            {
                neg=-1;
                n=scan();
            }
            while(!isWhiteSpace(n))
            {
                if(n>='0'&&n<='9')
                {
                    integer*=10;
                    integer+=n-'0';
                    n=scan();
                }
                else throw new InputMismatchException();
            }
            return neg*integer;
        }
        public double scanDouble()throws IOException
        {
            double doub=0;
            int n=scan();
            while(isWhiteSpace(n))
                n=scan();
            int neg=1;
            if(n=='-')
            {
                neg=-1;
                n=scan();
            }
            while(!isWhiteSpace(n)&&n!='.')
            {
                if(n>='0'&&n<='9')
                {
                    doub*=10;
                    doub+=n-'0';
                    n=scan();
                }
                else throw new InputMismatchException();
            }
            if(n=='.')
            {
                n=scan();
                double temp=1;
                while(!isWhiteSpace(n))
                {
                    if(n>='0'&&n<='9')
                    {
                        temp/=10;
                        doub+=(n-'0')*temp;
                        n=scan();
                    }
                    else throw new InputMismatchException();
                }
            }
            return doub*neg;
        }
        public String scanString()throws IOException
        {
            StringBuilder sb=new StringBuilder();
            int n=scan();
            while(isWhiteSpace(n))
                n=scan();
            while(!isWhiteSpace(n))
            {
                sb.append((char)n);
                n=scan();
            }
            return sb.toString();
        }
        private boolean isWhiteSpace(int n)
        {
            if(n==' '||n=='\n'||n=='\r'||n=='\t'||n==-1)
                return true;
            return false;
        }
    }
}


Measured memory_bytes: 32352