//要么一个点有两个father，要么根有father，暴力验证一下这几条可能的边就出来了#include<cstdio>#include<vector>using namespace std;const int N=1e5+5;int n,a[N],b[N];vector<int>fa[N];int main(){    scanf("%d",&n);    for(int i=1;i<=n;i++) scanf("%d%d",a+i,b+i);    for(int i=1;i<=n;i++){        if(a[i]==b[i]){printf("%d\n",i);return 0;}        if(1==b[i]){printf("%d\n",i);return 0;}        fa[b[i]].push_back(i);    }    for(int i=1;i<=n;i++) if(fa[i].size()>1){        printf("%d %d\n",fa[i][0],fa[i][1]);        return 0;    }    return 0;}