#include <bits/stdc++.h>
#pragma GCC diagnostic ignored "-Wincompatible-pointer-types"
typedef struct {
  int32_t a;
  int32_t b;
} hw;
typedef struct {
  int64_t a;
  int64_t b;
} hwll;
typedef struct {
  int64_t a;
  int64_t b;
  int64_t c;
} hwllc;
typedef struct {
  hwll a;
  hwll b;
} linell;
uint64_t n, m;
uint64_t h, w;
uint64_t k;
uint64_t q;
int64_t va, vb, vc, vd, ve, vf;
uint64_t ua, ub, uc, ud, ue, uf;
long double vra, vrb, vrc;
double vda, vdb, vdc;
char ch, dh;
uint64_t umin(uint64_t x, uint64_t y) { return (x < y) ? x : y; }
uint64_t umax(uint64_t x, uint64_t y) { return (x > y) ? x : y; }
int64_t smin(int64_t x, int64_t y) { return (x < y) ? x : y; }
int64_t smax(int64_t x, int64_t y) { return (x > y) ? x : y; }
uint64_t gcd(uint64_t x, uint64_t y) {
  if (x < y) {
    return gcd(y, x);
  } else if (y == 0) {
    return x;
  } else {
    return gcd(y, x % y);
  }
}
uint64_t bitpow(uint64_t a, uint64_t x, uint64_t modulo) {
  uint64_t result = 1;
  while (x) {
    if (x & 1) {
      result *= a;
      result %= modulo;
    }
    x /= 2;
    a = (a * a) % modulo;
  }
  return result;
}
uint64_t divide(uint64_t a, uint64_t b, uint64_t modulo) {
  return (a * bitpow(b, modulo - 2, modulo)) % modulo;
}
uint64_t udiff(uint64_t a, uint64_t b) {
  if (a >= b) {
    return a - b;
  } else {
    return b - a;
  }
}
int64_t sdiff(int64_t a, int64_t b) {
  if (a >= b) {
    return a - b;
  } else {
    return b - a;
  }
}
int bitcount(uint64_t n) {
  int result = 0;
  while (n) {
    if (n & 1) result++;
    n /= 2;
  }
  return result;
}
int32_t pullcomp(const void *left, const void *right) {
  uint64_t l = *(uint64_t *)left;
  uint64_t r = *(uint64_t *)right;
  if (l < r) {
    return -1;
  }
  if (l > r) {
    return +1;
  }
  return 0;
}
int32_t psllcomp(const void *left, const void *right) {
  int64_t l = *(int64_t *)left;
  int64_t r = *(int64_t *)right;
  if (l < r) {
    return -1;
  }
  if (l > r) {
    return +1;
  }
  return 0;
}
int32_t pcharcomp(const void *left, const void *right) {
  char l = *(char *)left;
  char r = *(char *)right;
  if (l < r) {
    return -1;
  }
  if (l > r) {
    return +1;
  }
  return 0;
}
int32_t pdoublecomp(const void *left, const void *right) {
  double l = *(double *)left;
  double r = *(double *)right;
  if (l < r) {
    return -1;
  }
  if (l > r) {
    return +1;
  }
  return 0;
}
int32_t pstrcomp(const void *left, const void *right) {
  char *l = *(char **)left;
  char *r = *(char **)right;
  return strcmp(l, r);
}
int32_t phwllABcomp(const void *left, const void *right) {
  hwll l = *(hwll *)left;
  hwll r = *(hwll *)right;
  if (l.a < r.a) {
    return -1;
  }
  if (l.a > r.a) {
    return +1;
  }
  if (l.b < r.b) {
    return -1;
  }
  if (l.b > r.b) {
    return +1;
  }
  return 0;
}
int32_t phwllREVcomp(const void *left, const void *right) {
  hwll l = *(hwll *)left;
  hwll r = *(hwll *)right;
  if (l.b < r.b) {
    return -1;
  }
  if (l.b > r.b) {
    return +1;
  }
  if (l.a < r.a) {
    return -1;
  }
  if (l.a > r.a) {
    return +1;
  }
  return 0;
}
int32_t ptriplecomp(const void *left, const void *right) {
  hwllc l = *(hwllc *)left;
  hwllc r = *(hwllc *)right;
  if (l.a < r.a) {
    return -1;
  }
  if (l.a > r.a) {
    return +1;
  }
  if (l.b < r.b) {
    return -1;
  }
  if (l.b > r.b) {
    return +1;
  }
  if (l.c < r.c) {
    return -1;
  }
  if (l.c > r.c) {
    return +1;
  }
  return 0;
}
bool isinrange(int64_t left, int64_t x, int64_t right) {
  return (left <= x && x <= right);
}
bool isinrange_soft(int64_t left, int64_t x, int64_t right) {
  return (left <= x && x <= right) || (left >= x && x >= right);
}
int64_t a[1000000];
int64_t b[1000000];
int64_t c[1000000];
char s[1000000 + 1];
char t[1000000 + 1];
hwll sorted[1000000];
uint64_t solen[1000000];
bool dp[2][6000];
int64_t dfs(uint64_t v) {
  int64_t i, j;
  for (i = 0; i <= b[v]; i++) {
    dp[0][i] = (i ? false : true);
  }
  uint64_t curr = 0;
  uint64_t total = 0;
  for (i = solen[v]; i < solen[v + 1]; i++) {
    uint64_t u = sorted[i].b;
    int64_t ret = dfs(u);
    if (ret < 0) return -1;
    total += (ret + b[u]);
    for (j = 0; j <= b[v]; j++) {
      if ((j >= ret && dp[curr][j - ret]) ||
          (j >= b[u] && dp[curr][j - b[u]])) {
        dp[curr ^ 1][j] = true;
      } else {
        dp[curr ^ 1][j] = false;
      }
    }
    curr ^= 1;
  }
  for (i = b[v]; i >= 0; i--) {
    if (dp[curr][i]) break;
  }
  if (i < 0) return -1;
  return total - i;
}
uint64_t solve() {
  int64_t i, j, ki, li;
  uint64_t result = 0;
  double dresult = 0;
  int64_t maybe = 0;
  int64_t sum = 0;
  int64_t item;
  uint64_t *dpcell;
  for (i = 0; i < n - 1; i++) {
    sorted[i].a = a[i + 1];
    sorted[i].b = i + 1;
  }
  qsort(sorted, (n - 1), sizeof(hwll), phwllABcomp);
  i = 0;
  j = 0;
  while (i < n) {
    solen[i] = j;
    while (j < (n - 1) && sorted[j].a == i) j++;
    i++;
  }
  solen[n] = n - 1;
  int64_t r = dfs(0);
  if (r < 0) {
    printf("IM");
  }
  puts("POSSIBLE");
  return 0;
success:
  puts("Yes");
  return 0;
fail:
  puts("No");
  return 1;
}
int32_t main(void) {
  int32_t i, j;
  int32_t x, y;
  scanf("%llu", &n, &m);
  for (i = 1; i < n; i++) {
    scanf("%lld", &a[i]);
    a[i]--;
  }
  for (i = 0; i < n; i++) {
    scanf("%lld", &b[i]);
  }
  solve();
  return 0;
}
