Here is my code:

#include <iostream>

using namespace std;

int x[200];

int compare (const void *a, const void *b)
{
    return (*(int*)a - *(int*)b);
}

int main()
{
    int r[200], a = 3;
    long min;
    bool z = false;
    for (int  i = 0; i<3; i++)
        cin>>x[i];
    for ( ; ; )
    {
        qsort (x, a, sizeof(int), compare);
        min = 1000000000;
        for (int i = 0; i<a-1; i++)
        {
            r[i] = abs(x[i] - x[i+1]);
            if (r[i]<min)
                min = r[i];
        }
        x[a] = min;
        for (int j = 0; j<a; j++)
        {
            if (x[j] == min)
            {
                z = true;
                break;
            }
        }
        if (z == true) break;
        a++;
    }
    printf("%d", a - 1);
    return 0;
}

Where is my mistake?

Use long long instead of int