#include<iostream>

using namespace std;

#define prep(i,a,b) for(int i = (a); i <= (b); i ++)
#define rrep(i,a,b) for(int i = (a); i >= (b); i --)

typedef long long LL;
const char nl = '\n';
int T, n, m;
char a[11];
int aw,bw,ar = 5,br = 5;

void solve() {
    aw = 0,bw = 0,ar = 5,br = 5;	//每次需要进行初始化
	cin >> a + 1;	//字符串的输入
	prep(i,1,10){
	//奇偶判断AB
		if(i%2)ar--;	//罚球机会--
		else br--;

		if(a[i] == '1'){
			if(i%2)aw++;	//进球数++
			else bw++;
		}
        if(aw > bw + br || bw > aw + ar){
            cout << i << nl;
            return;
        }
	}
	if(aw == bw)cout << -1 << nl;

}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);

	cin >> T;
	while (T--) {
		solve();
	}

	return 0;
}