//最小頂點割集
#define MAXN 100
#define inf 1000000000

int max_flow(int n,int mat[][MAXN],int source,int sink){
	int v[MAXN],c[MAXN],p[MAXN],ret=0,i,j;
	for (;;){
		for (i=0;i<n;i++)
			v[i]=c[i]=0;
		for (c[source]=inf;;){
			for (j=-1,i=0;i<n;i++)
				if (!v[i]&&c[i]&&(j==-1||c[i]>c[j]))
					j=i;
			if (j<0) return ret;
			if (j==sink) break;
			for (v[j]=1,i=0;i<n;i++)
				if (mat[j][i]>c[i]&&c[j]>c[i])
					c[i]=mat[j][i]<c[j]?mat[j][i]:c[j],p[i]=j;
		}
		for (ret+=j=c[i=sink];i!=source;i=p[i])
			mat[p[i]][i]-=j,mat[i][p[i]]+=j;
	}
}

int min_vertex_cut(int n,int mat[][MAXN],int source,int sink,int* set){
	int m0[MAXN][MAXN],m[MAXN][MAXN],i,j,k,ret=0,last;
	if (source==sink||mat[source][sink])
		return -1;
	for (i=0;i<n+n;i++)
		for (j=0;j<n+n;j++)
			m0[i][j]=0;
	for (i=0;i<n;i++)
		for (j=0;j<n;j++)
			if (mat[i][j])
				m0[i][n+j]=inf;
	for (i=0;i<n;i++)
		m0[n+i][i]=1;
	for (i=0;i<n+n;i++)
		for (j=0;j<n+n;j++)
			m[i][j]=m0[i][j];
	last=max_flow(n+n,m,source,n+sink);
	for (k=0;k<n&&last;k++)
		if (k!=source&&k!=sink){
			for (i=0;i<n+n;i++)
				for (j=0;j<n+n;j++)
					m[i][j]=m0[i][j];
			m[n+k][k]=0;
			if (max_flow(n+n,m,source,n+sink)<last){
				set[ret++]=k;
				m0[n+k][k]=0;
				last--;
			}
		}
	return ret;
}