here is my code. please help me :((

#include <stdio.h>
#define HMAX (1<<17)

int N;
unsigned int H[HMAX];

void sift(int x)
{
        int aux, up = x>>1;

        if (x < 1) return;

        if (H[x] > H[up])
        {
           aux = H[x]; H[x] = H[up]; H[up] = aux;
           sift(up);
        }
}

void perc(int x, int n)
{
        int l = x<<1, r = (x<<1)+1, max, aux;

        if (r > n) return;

        max = l;
        if (H[l] < H[r]) max = r;

        if (H[max] > H[x])
        {
           aux = H[max]; H[max] = H[x]; H[x] = aux;
           perc(max, 1+N/2);
        }
}

int main()
{
        int i, val;
        long double sol;
        unsigned int last, blast;

//        freopen("1306.in", "r", stdin);
        scanf("%d", &N);

        H[0] = 4294967295;

        for (i = 1; i <= 1+(N/2); i++)
                scanf("%lu", H+i);
        for (i = 1; i <= 1+(N/2); i++) sift(i);

        for (i = 2+(N/2); i <= N; i++)
        {
                scanf("%d", &val);
                if (val < H[1]) { H[1] = val; perc(1, 1+(N/2)); }
        }


        blast = H[1];
        H[1] = 0;
        perc(1, (N/2));
        last = H[1];

        sol = last*0.5;
        sol += blast*0.5;
        if ( (N&1) == 0 ) printf("%0.1llf\n", sol);
        else printf("%u\n", blast);

        return 0;

}

please help me

Try test with n=2.
FE
2
10
20

The result of my Program is 15.0
How about you ??

In my opinion, test #2 contain data like this:
1
5

Correct answer is:
5.0

I had a problem with output format. We should output the answer with one decimal digit after decimal point. My wrong program had written:
5
without fractional part.