题解（vector）

#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;


int main(){
    int n,m,ord;
    vector<int> node;
    cin>>n>>m;
    while(n--){
        int x;
        cin>>x;
        node.push_back(x);
    }
    while(m--){
        int x;
        cin>>x;
        node.erase(find(node.begin(),node.end(),x));
    }
    cin>>ord;
    for (int i=0;i<node.size();++i){
        if (node[i]==ord){cout<<i+1;return 0;}
    }
    throw "Not found";
    return 1;
}