Output each password is or not acceptable

Easier Done Than Said

#include <fstream>
#include <iostream>
using namespace std;
//Output each password is or not acceptable.
int main()
{
    //ifstream cin("easier_done_than_said.txt");
    string s;
    int a,b;    //count of consecutive vowels and consonants
    bool c1,c2,c3,is;   //fill rules 1-3 and consecutive or not
    string vs="aeiou";
    while(cin>>s)
    {   
        if(s=="end") break;
        c1=is=false;c2=c3=true;a=b=1;
        for(int i=0;i<s.length();i++)
        {
            int n=vs.find(s[i]);    //index of vowel
            if(n!=-1)
            {
                if(is) a++;
                if(a>2) c2=false;   //more than 2 consecutive vowels
                c1=true;    //at least one vowel
                b=1;is=true;
            }
            else
            {
                if(!is) b++;
                if(b>2) c2=false;   //more than 2 consecutive consonants
                a=1;is=false;
            }
            if(i>0&&s[i]==s[i-1]&&n%2!=1)   //two consecutive and same letter
                c3=false;
        }
        if(c1&&c2&&c3)
            cout<<"<"<<s<<"> is acceptable."<<endl;
        else
            cout<<"<"<<s<<"> is not acceptable."<<endl;
    }   
    return 0;
}