#include <iostream>
#include <algorithm>
#include "string"
#include "vector"
#include "stack"
#include "set"
using namespace std;
int singleNumber(vector<int>& nums)
{
int res = 0;
for (int i = 0; i < nums.size(); i++)
{
res = res^nums[i];
}
return res;
}
int main()
{
vector<int>v1;
v1.push_back(2);
v1.push_back(2);
v1.push_back(1);
cout<<singleNumber(v1);
system("pause");
return 0;
}