单词的长度

#include<iostream>
#include<string>
#include<cstring>
#include<cctype>
using namespace std;
int main()
{
string s;
int l=0,n=0;
getline(cin,s);
for(int i=0;i<s.length();i++)
{
if(isalpha(s[i])){
l++;
}
if(isalpha(s[i])&&!isalpha(s[i+1]))
n++;
}
cout<<l/(double)n<<endl;
}