#include<bits/stdc++.h>
#define For(i,l,r) for(register int i=(l);i<=(r);++i)
#define For_down(i,r,l) for(register int i=(r);i>=(l);--i)
using namespace std;
const int n_MAX=1000000+5;
int n,ans;
char s[2][n_MAX];
char t[2][n_MAX];
int p[2],c[2][2];
inline void go(const int i)
{
    For(j,0,1) c[!i][!j]-=c[i][j],c[i][j]=0;
    while(true)
    {
        ++p[i];
        ++c[i][s[i][p[i]]-'0'];
        if(t[i][p[i]]=='0')
        {
            break;
        }
    }
}
inline void insert(const int i)
{
    ++c[i][s[i][p[i]]-'0'];
}
inline void remove(const int i)
{
    --c[i][s[i][p[i]]-'0'];
}
inline bool match()
{
    return (s[0][p[0]]==s[1][p[1]]);
}
int main()
{
    freopen("edit.in","r",stdin);
    freopen("edit.out","w",stdout);
    ios::sync_with_stdio(0),cin.tie(0);
    int T; cin>>T;
    while(T--)
    {
        cin>>n,ans=0;
        For(i,0,1) cin>>(s[i]+1),s[i][n+1]='0';
        For(i,0,1) cin>>(t[i]+1),t[i][n+1]='0';
        memset(p,0,sizeof(p));
        memset(c,0,sizeof(c));
        go(0);
        go(1);
        while(true)
        {
            if(p[0]==p[1]) ans+=match(),remove(0),remove(1);
            else if(p[0]<p[1]) remove(1);
            else if(p[0]>p[1]) remove(0);
            For(i,0,1)
            {
                const int x=min(c[0][i],c[1][i]);
                ans+=x,c[0][i]-=x,c[1][i]-=x;
            }
            if(min(p[0],p[1])==(n+1)) break;
            if(p[0]==p[1]) memset(c,0,sizeof(c)),go(0),go(1);
            else if(p[0]<p[1]) go(0),insert(1);
            else if(p[0]>p[1]) go(1),insert(0);
        }
        cout<<(ans-1)<<'\n';
    }
    return 0;
}