Problem:
Score: 200 points

Problem Statement

Takahashi will do a tap dance. The dance is described by a string S where each character is L, R, U, or D. These characters indicate the positions on which Takahashi should step. He will follow these instructions one by one in order, starting with the first character.

S is said to be easily playable if and only if it satisfies both of the following conditions:

Every character in an odd position (1-st, 3-rd, 5-th, \ldots) is R, U, or D.

Every character in an even position (2-nd, 4-th, 6-th, \ldots) is L, U, or D.

Your task is to print Yes if S is easily playable, and No otherwise.

Constraints

S is a string of length between 1 and 100 (inclusive).

Each character of S is L, R, U, or D.

Input

Input is given from Standard Input in the following format:

S

Output

Print Yes if S is easily playable, and No otherwise.

Sample Input 1

RUDLUDR

Sample Output 1

Yes

Every character in an odd position (1-st, 3-rd, 5-th, 7-th) is R, U, or D.

Every character in an even position (2-nd, 4-th, 6-th) is L, U, or D.

Thus, S is easily playable.

Sample Input 2

DULL

Sample Output 2

No

The 3-rd character is not R, U, nor D, so S is not easily playable.

Sample Input 3

UUUUUUUUUUUUUUU

Sample Output 3

Yes

Sample Input 4

ULURU

Sample Output 4

No

Sample Input 5

RDULULDURURLRDULRLR

Sample Output 5

Yes

Solution in C (Clang 3.8.0) (judge verdict: Accepted)

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
#include <ctype.h>
#include <stdint.h>
#include <string.h>
#include <wchar.h>
#include <math.h>

#define N_MAX (100)
#define P_MAX (100)
#define DP_ARRAY_SIZE (N_MAX * P_MAX / 32 + 1)

#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define ABS(a) ((a) < 0 ? -(a) : (a))
#define ABSS(a, b) ((a) > (b) ? (a) - (b) : (b) - (a))

int compare_sz_asc(const void* a, const void* b) {
    return *((size_t*)a) < *((size_t*)b) ? -1 : 1;
}

int compare_sz_desc(const void* a, const void* b) {
    return *((size_t*)a) > * ((size_t*)b) ? -1 : 1;
}

int compare_i64_asc(const void* a, const void* b) {
    return *((int64_t*)a) < *((int64_t*)b) ? -1 : 1;
}

int compare_i64_desc(const void* a, const void* b) {
    return *((int64_t*)a) > * ((int64_t*)b) ? -1 : 1;
}

int compare_u64_asc(const void* a, const void* b) {
    return *((uint64_t*)a) < *((uint64_t*)b) ? -1 : 1;
}

int compare_u64_desc(const void* a, const void* b) {
    return *((uint64_t*)a) > * ((uint64_t*)b) ? -1 : 1;
}

int compare_c_asc(const void* a, const void* b) {
    return *((char*)a) < *((char*)b) ? -1 : 1;
}

int compare_c_desc(const void* a, const void* b) {
    return *((char*)a) > * ((char*)b) ? -1 : 1;
}

int compare_dp_asc(const void* a, const void* b) {
    return *((double*)a) < *((double*)b) ? -1 : 1;
}

static size_t powSz(const size_t base, const size_t exp) {
    if (exp == 0) {
        return 1;
    }

    if (exp == 1) {
        return base;
    }

    if (exp % 2 == 0) {
        return powSz(base * base, exp / 2);
    }
    else {
        return base * powSz(base, exp - 1);
    }
}

static size_t comb(const size_t n, const size_t r) {
    size_t result = 1;

    for (size_t i = 0; i < r; i++) {
        result *= n - i;
        result /= i + 1;
    }

    return result;
}

static uint64_t combU64(const uint64_t n, const uint64_t r) {
    uint64_t result = 1;

    for (uint64_t i = 0; i < r; i++) {
        result *= n - i;
        result /= i + 1;
    }

    return result;
}

static size_t gcdZu(size_t m, size_t n) {
    size_t temp;

    while (m % n != 0) {
        temp = n;
        n = m % n;
        m = temp;
    }

    return n;
}

static uint64_t gcdU64(uint64_t m, uint64_t n)
{
    uint64_t temp;

    while (m % n != 0) {
        temp = n;
        n = m % n;
        m = temp;
    }

    return n;
}

typedef struct {
    uint64_t A;
    uint64_t B;
    uint64_t val;
} _status;

static _status status[200000];

typedef struct {
    uint64_t idx;
}BHeap_Val;

#define BHEAP_VAL_TYPE BHeap_Val

static int _bHeap_Compare(const BHEAP_VAL_TYPE* parent, const BHEAP_VAL_TYPE* node) {
    const uint64_t parentVal = status[parent->idx].val;
    const uint64_t nodeVal = status[node->idx].val;

    return parentVal >= nodeVal ? -1 : 1;
}

#define BHEAP_INVALID_NODE ((size_t)100000000)

typedef struct {
    BHEAP_VAL_TYPE val;
} BHeap_Node;

static struct {
    size_t size;
    int (*compare)(const BHEAP_VAL_TYPE* parent, const BHEAP_VAL_TYPE* node);
} bHeap_Info;
static BHeap_Node bHeap_Node[1 << 20];

static void bHeap_Init(int(*compare)(const BHEAP_VAL_TYPE* parent, const BHEAP_VAL_TYPE* node)) {
    bHeap_Info.size = 0;
    bHeap_Info.compare = compare;
}

static void bHeap_UpHeap(const size_t nodeIdx) {
    if (nodeIdx == 0) {
        return;
    }

    const size_t parentIdx = (nodeIdx + 1) / 2 - 1;

    const int compareResult = bHeap_Info.compare(&(bHeap_Node[parentIdx].val), &(bHeap_Node[nodeIdx].val));

    if (0 < compareResult) {
        const BHEAP_VAL_TYPE tmp = bHeap_Node[parentIdx].val;
        bHeap_Node[parentIdx].val = bHeap_Node[nodeIdx].val;
        bHeap_Node[nodeIdx].val = tmp;

        if (parentIdx != 0) {
            bHeap_UpHeap(parentIdx);
        }
    }
}

static void bHeap_DownHeap(const size_t nodeIdx) {
    if (bHeap_Info.size - 1 <= nodeIdx) {
        return;
    }

    const size_t leftIdx = 2 * (nodeIdx + 1) - 1;

    if (leftIdx < bHeap_Info.size) {
        const int leftResult = bHeap_Info.compare(&(bHeap_Node[nodeIdx].val), &(bHeap_Node[leftIdx].val));

        size_t swapTarget = leftResult < 0 ? BHEAP_INVALID_NODE : leftIdx;

        const size_t rightIdx = leftIdx + 1;

        if (rightIdx < bHeap_Info.size) {
            const int rightResult = bHeap_Info.compare(&(bHeap_Node[nodeIdx].val), &(bHeap_Node[rightIdx].val));

            if (swapTarget == BHEAP_INVALID_NODE) {
                if (0 < rightResult) {
                    swapTarget = rightIdx;
                }
            }
            else {
                if (0 < rightResult) {
                    const int rightLeftResult = bHeap_Info.compare(&(bHeap_Node[leftIdx].val), &(bHeap_Node[rightIdx].val));

                    if (0 < rightLeftResult) {
                        swapTarget = rightIdx;
                    }
                }
            }
        }

        if (swapTarget != BHEAP_INVALID_NODE) {
            const BHEAP_VAL_TYPE tmp = bHeap_Node[nodeIdx].val;
            bHeap_Node[nodeIdx].val = bHeap_Node[swapTarget].val;
            bHeap_Node[swapTarget].val = tmp;

            bHeap_DownHeap(swapTarget);
        }
    }
}

static void bHeap_Add(const BHEAP_VAL_TYPE val) {
    bHeap_Node[bHeap_Info.size].val = val;

    bHeap_Info.size++;

    bHeap_UpHeap(bHeap_Info.size - 1);
}

static void bHeap_RemoveTop(void) {
    if (bHeap_Info.size == 0) {
        return;
    }

    if (bHeap_Info.size == 1) {
        bHeap_Info.size--;
        return;
    }

    bHeap_Node[0].val = bHeap_Node[bHeap_Info.size - 1].val;

    bHeap_Info.size--;

    bHeap_DownHeap(0);
}

static BHEAP_VAL_TYPE* bHeap_GetTopVal(void) {
    return bHeap_Info.size == 0 ? NULL : &(bHeap_Node[0].val);
}

typedef struct {
    uint64_t cnt;
    size_t* child;
    size_t numChild;
    size_t maxNumChild;
} Tree_Node;

#define TREE_INIT_ALLOC (128)

static Tree_Node tree_Node[200000];

static void tree_Init(const uint64_t N) {
    for (uint64_t i = 0; i < N; i++) {
        tree_Node[i].cnt = 0;
        tree_Node[i].numChild = 0;
        tree_Node[i].child = malloc(sizeof(size_t) * TREE_INIT_ALLOC);
        tree_Node[i].maxNumChild = TREE_INIT_ALLOC;
    }
}

static void tree_AddChild(const size_t parent, const size_t child) {
    if (tree_Node[parent].maxNumChild <= tree_Node[parent].numChild) {
        tree_Node[parent].child = realloc(tree_Node[parent].child, sizeof(size_t) * tree_Node[parent].maxNumChild * 2);
        tree_Node[parent].maxNumChild *= 2;
    }

    tree_Node[parent].child[tree_Node[parent].numChild] = child;
    tree_Node[parent].numChild++;
}

int main(void) {
    char S[101];

    scanf("%s", S);

    const size_t len = strlen(S);

    for (size_t i = 0; i < len; i++) {
        if (i % 2 == 0) {
            if (S[i] == 'L') {
                puts("No");
                return 0;
            }
        }
        else {
            if (S[i] == 'R') {
                puts("No");
                return 0;
            }
        }
    }

    puts("Yes");

    return 0;
}