/** * author: TakeruOkuyama * created: 2020-04-09 14:53:46 **/ #include <bits/stdc++.h> #define rep(i, n) for(int i = 0; i < (n); i++) using namespace std; using ll = long long; using P = pair<int, int>; const int MOD = 1000000007; int main(){ vector<int> B(9); rep(i, 9){ cin >> B[i]; } rep(i, 9){ if(B[i] != i + 1){ cout << i + 1 << endl; return 0; } } return 0;} /** * g++ code.cpp * ./a.out * shift + ctrl + i **/