#include<cstdio>

#include<algorithm>

#include<cstring>

using namespace std;

const int maxn = 500+10;

const int maxm = 50000 + 10;

const int inf = 0x3f3f3f3f;

int g[maxn],v[maxm],f[maxm],c[maxm],nex[maxm],eid;

int id[maxn][2],vid;

int n,ans,S,T;

bool inque[maxn];

int q[maxm],dist[maxn],pre[maxn];

void addedge(int a,int b,int F,int C) {

    v[eid]=b; f[eid]=F; c[eid]=C; nex[eid]=g[a]; g[a]=eid++;

    v[eid]=a; f[eid]=0; c[eid]=-C; nex[eid]=g[b]; g[b]=eid++;

}

bool build() {

    if(scanf("%d",&n)==1&&n) {

        memset(g,-1,sizeof(g)); eid=0; vid=0;

        S=++vid; T=++vid;

        for(int i=1;i<=n;i++) {

            id[i][0]=++vid;

            id[i][1]=++vid;

            addedge(S,id[i][0],1,0);

            addedge(id[i][1],T,1,0);

        }

        for(int i=1,j,d;i<=n;i++)

            while(scanf("%d",&j) && j) {

                scanf("%d",&d);

                addedge(id[i][0],id[j][1],1,d);

            }

        return true;

    }

    return false;

}

bool SPFA() {

    int u,l,r;

    l=r=0;

    memset(dist,0x3f,sizeof(dist));

    dist[S]=0;

    inque[q[r++]=S]=1;

    while(l<r) {

        inque[u=q[l++]]=0;

        for(int i=g[u];~i;i=nex[i])

            if(f[i] && dist[v[i]]>dist[u]+c[i]) {

            dist[v[i]]=dist[u]+c[i];

            pre[v[i]]=i;

            if(!inque[v[i]]) inque[q[r++]=v[i]]=1;

        }

    }

    return dist[T]<inf;

}

int augment() {

    int aug=inf,res=0;

    for(int i=T;i!=S;i=v[pre[i]^1]) aug=min(aug,f[pre[i]]);

    for(int i=T;i!=S;i=v[pre[i]^1]) {

        f[pre[i]]-=aug;

        f[pre[i]^1]+=aug;

        res+=aug*c[pre[i]];

    }

    ans+=aug;

    return res;

}

void solve() {

    ans=0;

    int res=0;

    while(SPFA()) res+=augment();

    if(ans!=n) printf("N\n");

    else printf("%d\n",res);

}

int main() {

    while(build()) solve();

    return 0;

}