long long inverce(long long a, long long m)
{
long long x=0,y=0;
long long g=gcdex(a,m,x,y);
if (g!=1) return 0;
return x;
}
int gcdex(int a, int b, int *x, int *y) {
if (a == 0) {
*x = 0; *y = 1;
return b;
}
int x1, y1;
int d = gcdex(b%a, a, &x1, &y1);
*x = y1 - (b / a) * x1;
*y = x1;
return d;
}
long long gcdex (long long a, long long b, long long & x, long long & y)
{
if (a == 0)
{
x = 0;
y = 1;
return b;
}
long long x1, y1;
long long d = gcdex (b%a, a, x1, y1);
x = y1 - (b / a) * x1;
y = x1;
return d;
}
long gcd(long k, long * m , long * w)
{//ci¹g m ma byc malej¹cy
long **x= new long *[k];
for(long i=0;i<k;i++)
{
x[i]=new long[k];
for(long j=0;j<k;j++)
x[i][j]=0;
x[i][i]=1;
}
long id=gcdex(k,m,x,0,k-1,k);
for(long i=0;i<k;i++)
w[i]=x[id][i];
return m[id];
}
long gcdex(long k, long * m, long **x, long i,long o,long n)
{
if(i==o)
return i;
long r= m[i]/m[o];
m[i]-=r*m[o];
if(m[i])
{
for(long j=0;j<k;j++)
x[i][j]-=r*x[o][j];
o=i;
}
else
n--;
if(++i==k)i=0;
while(!m[i])if(++i==k)i=0;
return gcdex( k , m , x , i , o , n );
}
int main() {
freopen("inverse.in", "r", stdin);
freopen("inverse.out", "w", stdout);
int x, y, n, p;
scanf("%d%d", &n, &p);
if(n == 1) {
printf("-1\n");
} else {
int g = gcdex (p, n, &x, &y);
if (g != 1)
printf("-1\n");
else {
x = (x % n + n) % n;
printf("%d\n", x);
}
}
return 0;
}
