#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstdlib>
#include <cstring>

using namespace std;

#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define REP(i,n) FOR(i,0,n)

typedef long long ll;

int main(){
	int f[10] = {};
	
	REP(i,9){
		int n;
		scanf("%d", &n);
		f[n-1] = 1;
	}
	
	REP(i,10){
		if (f[i] == 0) printf("%d\n", i+1);
	}
	
	return 0;
}