#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

void print(auto a){
  cout << a;
}

void printL(auto a){
  cout << a << endl;
}

int main(){
  int sum = 10*(10+1)/2;
  int i;
  while(cin >> i){
    sum -= i;
  }
  printL(sum);
}