count number of words

#include<iostream>
#include<string>
using namespace std;
int count_word(string s)
{
int i,count=0,len;
len=s.size();
for(i=0;i<len-2;i++)
{

    if((s[i]==' '&&s[i+1]>='a'&&s[i+1]<='z'&&s[i+2]>='a'&&s[i+2]<='z')||(s[i]==' '&&s[i+1]>='A'&&s[i+1]<='Z'&&s[i+2]>='A'&&s[i+2]<='Z'))
        count++;
}
return count;
}
int main ()

{

   string s;
    cout << "Enter a string : ";
    getline(cin,s);
    int count_w=count_word(s);
if(s[0]==' ')cout<<count_w<<endl;
else
 cout<<count_w+1<<endl;

    return 0;
}