#include<iostream>#include<set>#include<string.h>#include<stdlib.h>#include<algorithm>#include<stdio.h>using namespace std;enum { SIZ = 10004,};struct Node { int pos; char author[12]; char type;};int num;Node tree[SIZ];int ptr[SIZ];unsigned step[SIZ];struct author_cmp { bool operator ()(const int&a, const int&b)const{ return strcmp(tree[a].author, tree[b].author) < 0; }};struct set_cmp { bool operator ()(const int&a, const int&b)const{ if (step[a] != step[b]) return step[a] < step[b]; return a < b; }}scmp;set<int, set_cmp> tab;int src, dst;void update(int p, int s, char t){ unsigned v = step[s] + 1; v += (tree[s].type!=t); if (step[p] == -1 || step[p] > v){ if (step[p] != -1) tab.erase(p); step[p] = v; tab.insert(p); tree[p].type = t; }}unsigned fun(){ tab.clear(); step[src] = 0; tab.insert(src); int nex; while(!tab.empty()){ src = *tab.begin(); tab.erase(tab.begin()); if (src == dst){ return step[dst]; } nex = (src+1)%num; update(nex, src, 0); nex = (src-1+num)%num; update(nex, src, 0); nex = ptr[(tree[src].pos+1)%num]; update(nex, src, 1); nex = ptr[(num+tree[src].pos-1)%num]; update(nex, src, 1); } return -1;}int readIn(){ if (scanf("%d%d%d", &num,&src,&dst) < 0) return 0; --src, --dst; memset(step, -1, sizeof(step)); for (int i=0; i<num; ++i){ ptr[i] = i; tree[i].type = 0; scanf("%s", tree[i].author); scanf("%s", tree[i].author); } sort(ptr, ptr+num, author_cmp()); for (int i=0; i<num; ++i){ tree[ptr[i]].pos = i; } return 1;}int main(){ while(readIn() > 0){ unsigned v = fun(); printf("%un", v); } return 0;}
