1 #include<cstdio>
  2 #include<cstdlib>
  3 #include<cstring>
  4 #include<iostream>
  5 #include<algorithm>
  6 using namespace std;
  7
  8 const int N=210,INF=(int)1e9;
  9 int n,len,tl,f[N],g[N],first[N];
 10 struct node{
 11     int x,y,next,tmp;
 12     bool bk;
 13 }a[N];
 14 struct point{
 15     int d,id;
 16 }tf[N],tg[N];
 17
 18 int maxx(int x,int y){return x>y ? x:y;}
 19 int minn(int x,int y){return x<y ? x:y;}
 20
 21 void ins(int x,int y,int tmp)
 22 {
 23     a[++len].x=x;a[len].y=y;a[len].tmp=tmp;a[len].bk=0;
 24     a[len].next=first[x];first[x]=len;
 25 }
 26
 27 bool cmp(point x,point y){return x.d<y.d;}
 28
 29 void dp(int x,int lim)
 30 {
 31     for(int i=first[x];i;i=a[i].next) dp(a[i].y,lim);
 32     tl=0;
 33     for(int i=first[x];i;i=a[i].next)
 34     {
 35         int y=a[i].y;
 36         if(a[i].tmp==2)
 37         {
 38             tl++;
 39             tf[tl].d=f[y];tf[tl].id=i;
 40             tg[tl].d=g[y];tg[tl].id=i;
 41         }
 42     }
 43     sort(tf+1,tf+1+tl,cmp);
 44     sort(tg+1,tg+1+tl,cmp);
 45     if(tl==0)
 46     {
 47         f[x]=0;g[x]=0;
 48         for(int i=first[x];i;i=a[i].next)
 49         {
 50             int y=a[i].y;
 51             if(a[i].tmp==1) f[x]=maxx(f[x],f[y]+1);
 52             if(a[i].tmp==0) g[x]=maxx(g[x],g[y]+1);
 53             if(f[x]+g[x]+1>lim) {f[x]=INF,g[x]=INF;break;}
 54         }
 55         if(!first[x]) f[x]=g[x]=INF;//debug
 56     }
 57     else
 58     {
 59         //find_f
 60         f[x]=INF;g[x]=INF;
 61         int ff,gg;
 62         for(int k=0;k<=tl;k++)
 63         {
 64             ff=0;gg=0;
 65             if(k>0) a[tf[k].id].bk=1;
 66             for(int i=first[x];i;i=a[i].next)
 67             {
 68                 int y=a[i].y;
 69                 if(a[i].tmp==1 || (a[i].tmp==2 && a[i].bk==1)) ff=maxx(ff,f[y]+1);
 70                 if(a[i].tmp==0 || (a[i].tmp==2 && a[i].bk==0)) gg=maxx(gg,g[y]+1);
 71             }
 72             if(ff+gg+1<=lim) f[x]=minn(f[x],ff);
 73         }
 74         for(int k=1;k<=tl;k++) a[tf[k].id].bk=0;
 75
 76
 77         for(int k=0;k<=tl;k++)
 78         {
 79             ff=0;gg=0;
 80             if(k>0) a[tg[k].id].bk=1;
 81             for(int i=first[x];i;i=a[i].next)
 82             {
 83                 int y=a[i].y;
 84                 if(a[i].tmp==1 || (a[i].tmp==2 && a[i].bk==0)) ff=maxx(ff,f[y]+1);
 85                 if(a[i].tmp==0 || (a[i].tmp==2 && a[i].bk==1)) gg=maxx(gg,g[y]+1);
 86             }
 87             if(ff+gg+1<=lim) g[x]=minn(g[x],gg);
 88         }
 89         for(int k=1;k<=tl;k++) a[tg[k].id].bk=0;
 90     }
 91     // printf("f %d = %d   g %d = %d\n",x,f[x],x,g[x]);
 92 }
 93
 94 bool check(int lim)
 95 {
 96     // printf("lim = %d\n",lim);
 97     dp(1,lim);
 98     return (f[1]<INF);
 99 }
100
101 int main()
102 {
103     freopen("a.in","r",stdin);
104     int n,y;
105     char ch;
106     while(1)
107     {
108         n=0;
109         len=0;
110         memset(first,0,sizeof(first));
111         while(1)
112         {
113             int x;
114             scanf("%d",&x);
115             if(x==0) break;
116             n=maxx(n,x);
117             while(1)
118             {
119                 scanf("%d%c",&y,&ch);
120                 n=maxx(n,y);
121                 if(y==0) break;
122                 if(ch=='d') ins(x,y,0);
123                 else if(ch=='u') ins(x,y,1);
124                 else ins(x,y,2);
125             }
126         }
127         if(n==0) break;
128         int l=0,r=n,mid;//debug 是n而不是n-1
129         while(l<r)
130         {
131             mid=(l+r)/2;
132             if(check(mid)) r=mid;
133             else l=mid+1;
134         }
135         printf("%d\n",l);
136     }
137     return 0;
138 }