#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define N 200
#define INF 0x3f3f3f3f3f3f3f3fLL
long long min(long long a, long long b) { return a < b ? a : b; }
int max(int a, int b) { return a > b ? a : b; }
int *ej[N], eo[N], n, k;
void append(int i, int j) {
int o = eo[i]++;
if (o >= 2 && (o & o - 1) == 0)
ej[i] = (int *) realloc(ej[i], o * 2 * sizeof *ej[i]);
ej[i][o] = j;
}
long long ww[N];
int dfs1(int p, int i, int d) {
int o, w;
if (--d == 0) {
ww[i]++;
return 1;
}
w = 0;
for (o = eo[i]; o--; ) {
int j = ej[i][o];
if (j != p)
w += dfs1(i, j, d);
}
ww[i] += w;
return w;
}
long long dp[N][N + 1]; int sz[N + 1];
void dfs2(int p, int i) {
int o, di, dj;
dp[i][0] = ww[i], dp[i][1] = 0, sz[i] = 1;
for (o = eo[i]; o--; ) {
int j = ej[i][o];
if (j != p) {
dfs2(i, j);
memset(dp[i] + sz[i] + 1, INF, sz[j] * sizeof *dp[i]);
for (di = sz[i]; di >= 0; di--) {
long long x = dp[i][di];
dp[i][di] = INF;
for (dj = sz[j]; dj >= 0; dj--) {
long long y = dp[j][dj];
if (di + dj < k) {
int d = di == 0 ? 0 : max(di, dj + 1);
dp[i][d] = min(dp[i][d], x + y);
}
}
}
sz[i] += sz[j];
}
}
}
int main() {
int h, i, j, d;
long long w;
scanf("%d%d", &n, &k);
for (i = 0; i < n; i++)
ej[i] = (int *) malloc(2 * sizeof *ej[i]);
for (h = 0; h < n - 1; h++) {
scanf("%d%d", &i, &j), i--, j--;
append(i, j), append(j, i);
}
for (i = 0; i < n; i++)
dfs1(-1, i, k);
w = 0;
for (i = 0; i < n; i++)
w += ww[i] /= 2;
w /= k;
dfs2(-1, 0);
for (d = 0; d < n; d++)
if (dp[0][d] == w) {
printf("YES\n");
printf("0\n");
return 0;
}
printf("NO\n");
printf("0\n");
return 0;
}
