#include<bits/stdc++.h>
#define rep(i,j,k) for(int i=j;i<=k;i++)
#define repp(i,j,k) for(int i=j;i>=k;i--)
#define pii pair<int,int>
#define mp make_pair
#define fir first
#define sec second
#define ls(x) (x<<1)
#define rs(x) ((x<<1)|1)
#define lowbit(i) (i&-i)
#define int long long
using namespace std;
typedef long long ll;
const int N=1e5+5,M=25,mo=998244353,inf=1e18+7;
const double PI=acos(-1);
void read(int &p){
    int x=0,w=1;
    char ch=getchar();
    while(!isdigit(ch)){
        if(ch=='-')w=-1;
        ch=getchar();
    }
    while(isdigit(ch)){
        x=(x<<3)+(x<<1)+ch-'0';
        ch=getchar();
    }
    p=x*w;
}
int T;
int n,f[M][M][M];
pii s[N];
bool check(int x,int y){
    return (x>=11||y>=11)&&abs(x-y)>=2;
}
void calc(int m){
    rep(i,0,m){
        rep(j,0,m){
            rep(k,0,m)
                f[i][j][k]=0;
        }
    }
    f[0][0][0]=1;
    rep(i,1,m){
        rep(j,0,m){
            rep(k,0,m){
                if(s[i].fir!=-1&&(s[i].fir!=j||s[i].sec!=k)&&(s[i].fir!=k||s[i].sec!=j))continue;
                if(j&&!check(j-1,k))f[i][j][k]+=f[i-1][j-1][k];
                if(k&&!check(j,k-1))f[i][j][k]+=f[i-1][j][k-1];
                f[i][j][k]%=mo;
            }
        }
    }
}
void solve(){
    read(n);
    rep(i,1,n)
        read(s[i].fir),read(s[i].sec);
    calc(min(n,22ll));
    if(n<=22){
        int ans=0;
        rep(i,0,n){
            rep(j,0,n)
                if(check(i,j))ans+=f[n][i][j],ans%=mo;
        }
        printf("%lld\n",ans);
        return;
    }
    if(n&1){
        puts("0");
        return;
    }
    int ans=f[22][11][11];
    rep(i,22,n){
        if(i&1){
            if(s[i].fir!=-1&&(abs(s[i].fir-s[i].sec)>1||s[i].fir+s[i].sec!=i)){
                puts("0");
                return;
            }
            ans*=2,ans%=mo;
        }
        else if(i==n){
            if(s[i].fir!=-1&&(abs(s[i].fir-s[i].sec)!=2||s[i].fir+s[i].sec!=i)){
                puts("0");
                return;
            }
        }
        else{
            if(s[i].fir!=-1&&(s[i].fir!=s[i].sec||2*s[i].fir!=i)){
                puts("0");
                return;
            }
        }
    }
    printf("%lld\n",ans);
}
signed main(){
    read(T);
    while(T--)
        solve();
    return 0;
}