What is wrong with this? Help me please. ))

#include<vector>
#include<cmath>
//#include<conio.h>
using namespace std;

int main()
{
    unsigned int i, n;
    unsigned long k;
    vector<char>a;
    scanf("%d", &n);
    for(i = 0; i < n; i++)
    {
        scanf("%U", &k);
        if (sqrt(8 * k - 7) - floor(sqrt(8 * k - 7)))
         a.push_back(0);
        else a.push_back(1);
    }
    for(int i =0; i < a.size(); i++)
        printf("%d ", a[i]);

//getch();
return 0;
}


Thanks ))