Problem p03247 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#define REP(i, a, n) for (int i = a; i <= n; ++i)
#define PER(i, a, n) for (int i = n; i >= a; --i)
#define hr putchar(10)
#define pb push_back
#define lc (o << 1)
#define rc (lc | 1)
#define mid ((l + r) >> 1)
#define ls lc, l, mid
#define rs rc, mid + 1, r
#define x first
#define y second
#define io std::ios::sync_with_stdio(false)
#define endl '\n'
#define DB(a)                                                                  \
  ({                                                                           \
    REP(__i, 1, n) cout << a[__i] << ',';                                      \
    hr;                                                                        \
  })
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
const int P = 1e9 + 7, INF = 0x3f3f3f3f;
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll qpow(ll a, ll n) {
  ll r = 1 % P;
  for (a %= P; n; a = a * a % P, n >>= 1)
    if (n & 1)
      r = r * a % P;
  return r;
}
ll inv(ll x) { return x <= 1 ? 1 : inv(P % x) * (P - P / x) % P; }
inline int rd() {
  int x = 0;
  char p = getchar();
  while (p < '0' || p > '9')
    p = getchar();
  while (p >= '0' && p <= '9')
    x = x * 10 + p - '0', p = getchar();
  return x;
}
// head

#ifdef ONLINE_JUDGE
const int N = 1e6 + 50;
#else
const int N = 1e2 + 10;
#endif

int n, a[N], b[N], d[N];
char s[N];

int main() {
  scanf("%d", &n);
  int c[2]{};
  REP(i, 1, n) {
    scanf("%d%d", a + i, b + i);
    ++c[a[i] + b[i] & 1];
  }
  if (c[0] != n && c[1] != n)
    return puts("-1"), 0;
  printf("%d\n", 31 + !!c[0]);
  REP(i, 0, 30) printf("%d ", 1 << i);
  if (c[0])
    printf("%d ", 1);
  hr;
  REP(i, 1, n) {
    int x = a[i], y = b[i];
    if (c[0])
      --x, s[31] = 'R';
    int f = 0;
    PER(i, 0, 30) {
      if (abs(x) < abs(y))
        swap(x, y), f ^= 1;
      if (x > 0)
        x -= 1 << i, s[i] = "RU"[f];
      else
        x += 1 << i, s[i] = "LD"[f];
    }
    puts(s);
  }
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#define REP(i, a, n) for (int i = a; i <= n; ++i)
#define PER(i, a, n) for (int i = n; i >= a; --i)
#define hr putchar(10)
#define pb push_back
#define lc (o << 1)
#define rc (lc | 1)
#define mid ((l + r) >> 1)
#define ls lc, l, mid
#define rs rc, mid + 1, r
#define x first
#define y second
#define io std::ios::sync_with_stdio(false)
#define endl '\n'
#define DB(a)                                                                  \
  ({                                                                           \
    REP(__i, 1, n) cout << a[__i] << ',';                                      \
    hr;                                                                        \
  })
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
const int P = 1e9 + 7, INF = 0x3f3f3f3f;
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll qpow(ll a, ll n) {
  ll r = 1 % P;
  for (a %= P; n; a = a * a % P, n >>= 1)
    if (n & 1)
      r = r * a % P;
  return r;
}
ll inv(ll x) { return x <= 1 ? 1 : inv(P % x) * (P - P / x) % P; }
inline int rd() {
  int x = 0;
  char p = getchar();
  while (p < '0' || p > '9')
    p = getchar();
  while (p >= '0' && p <= '9')
    x = x * 10 + p - '0', p = getchar();
  return x;
}
// head

const int N = 1e5 + 10;
int n, a[N], b[N], d[N];
char s[N];

int main() {
  scanf("%d", &n);
  int c[2]{};
  REP(i, 1, n) {
    scanf("%d%d", a + i, b + i);
    ++c[a[i] + b[i] & 1];
  }
  if (c[0] != n && c[1] != n)
    return puts("-1"), 0;
  printf("%d\n", 31 + !!c[0]);
  REP(i, 0, 30) printf("%d ", 1 << i);
  if (c[0])
    printf("%d ", 1);
  hr;
  REP(i, 1, n) {
    int x = a[i], y = b[i];
    if (c[0])
      --x, s[31] = 'R';
    int f = 0;
    PER(i, 0, 30) {
      if (abs(x) < abs(y))
        swap(x, y), f ^= 1;
      if (x > 0)
        x -= 1 << i, s[i] = "RU"[f];
      else
        x += 1 << i, s[i] = "LD"[f];
    }
    puts(s);
  }
}