for (int z = i+1; z < n; z++)
                    {
                        __int64 r = (((__int64)a[j][z])*a[d][i] - ((__int64)a[j][i])*a[d][z]);
                        a[j][z] = mod(r);
                    }
                    a[j][i] = 0;

                    for (int z = i; z < n; z++)
                    {
                        __int64 r = (((__int64)a[j][z])*a[d][i] - ((__int64)a[j][i])*a[d][z]);
                        a[j][z] = mod(r);
                    }

first get AC, but second WA9

by the way, mod(0) == 0

const int P = (1<<30)-17;

int mod(__int64 x)
{
    int r = x % P;
    if (r < 0)
        r += P;
    return r;
}

Edited by author 05.05.2007 18:49

n = 2
i = d = 0
j = 1

a:
1 1
1 1

First result:
1 1
0 0

Second result:
1 1
0 1

thank you very much!