#include <string.h>
#define N 5000
char critical[N];
int ii[N], ds[N][N], dd[N][N];
int find(int *ds, int i) {
return ds[i] < 0 ? i : (ds[i] = find(ds, ds[i]));
}
int join(int *ds, int i, int j) {
i = find(ds, i);
j = find(ds, j);
if (i == j)
return 0;
if (ds[i] > ds[j])
ds[i] = j;
else {
if (ds[i] == ds[j])
ds[i]--;
ds[j] = i;
}
return 1;
}
int n;
void Init(int n_) {
int i;
n = n_;
for (i = 0; i < n; i++) {
ii[i] = i;
memset(ds[i], -1, n * sizeof *ds[i]);
critical[i] = 1;
}
}
void Link(int i, int j) {
int u;
for (u = 0; u < n; u++) {
if (i == u || j == u)
continue;
if (!join(ds[u], i, j))
critical[u] = 0;
if (++dd[u][i] > 2)
critical[u] = 0;
if (++dd[u][j] > 2)
critical[u] = 0;
}
}
int CountCritical() {
int i, cnt;
cnt = 0;
for (i = 0; i < n; i++)
if (critical[i])
cnt++;
return cnt;
}
