WA in DYZIO

[rit2011021_sof]

#include<iostream>
#include<cstdio>
#include<climits>
using namespace std;
int p, r, len, t = 0;
int cal(string x,int f)
{
	p++;
	if(x[p] == '1') {
		t++;
		if(len<f) {
			len = f;
			r = t;
		}
		cal(x,f*2);
		cal(x,f*2);
	}
}
int main()
{
	int n;
	int q=0;
	while(q<10)
	{
		cin>>n;
		string x;
		cin>>x;
		p=-1;
		r=0;
		len=INT_MIN;
		t=0;
		cal(x,1);
		cout<<r<<endl;
		q++;
	}
}