My program is correct but i have WA on test 6!!!

#include <iostream>
#include <string>
using namespace std;
int main ()
{
    string s,s1="tram",s2="trolleybus";
    int tram=0,trolleybus=0,i,n;
    while (cin>>s)
    {
            if (s==s1) tram++;
            if (s==s2) trolleybus++;
    }
    if (tram>trolleybus) cout<<"Tram driver"<<endl;
    if (tram==trolleybus) cout<<"Bus driver"<<endl;
    if (tram<trolleybus) cout<<"Trolleybus driver"<<endl;
}