#!/usr/local/gnu/bin/bash
read n
w=(`tr a a`)
if((`echo ${w[@]} | tr ' ' '\n' | sort -u | wc -l`!=n))
then
    echo No
    exit
fi
for i in `seq $((n-1))`
do
    if [ ${w[i-1]: -1} != ${w[i]:0:1} ]
    then
        echo No
        exit
    fi
done
echo Yes