class Solution {
public:
int getMissingNumber(vector[HTML_REMOVED]& nums) {
if(nums.empty()) return 0;
int sum=0,p,t,n;
n=nums.size();
for(int i=0;i<n;i++)
{
sum+=nums[i];
}
p=0.5(n+1)(0+n);
t=p-sum;
return t;
}
};