Language: C++

//Robs Code
/***********HEADER***************/
#include <iostream>
#include <bitset>
#include <deque>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <string>
#include <algorithm>
#include <list>
#include <vector>
#include <unordered_set>
#include <unordered_map>
#include <stack>
#include <set>
#include <queue>
#include <map>
/***********MACROS***************/
#define int long long int
#define fri(l,k) for (i=l;i<=k;i++)
#define frj(l,k) for (j=l;j>=k;j--)
#define fij(a,b,l,k) for(i=a;i<=b;i++) for(j=l;j<=k;j++)
#define all(x) x.begin(),x.end()
#define allr(x) x.rbegin(),x.rend()
#define endl "\n"
#define pb push_back
#define _1 first
#define _2 second
#define mxsz 1000000007
#define mxval 1e9 + 7
#define grt [](auto x,auto y){return x>y;}
#define pii pair<int,int>
/*********VARIABLE****************/
using namespace std;
int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
/*********FUNCTIONS**************/
int powom(int a,int b) {
    int result = 1;
    while (b > 0) {
        if (b & 1)
            result = result * a;
        a = a * a;
        b >>= 1;
    }
    return result;
}
/***********MAIN**************/
signed main(){
    ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
    string s;
    cin>>s;
    for(int i=0;i<s.length();i++){
        if((i+1)%2==0&&s[i]=='R'){
            cout<<"No";
            return 0;
        }
        if((i+1)%2!=0&&s[i]=='L'){
            cout<<"No";
            return 0;
        }
    }
    cout<<"Yes";
    return 0;
}
//.........//Robs Code
/***********HEADER***************/
#include <iostream>
#include <bitset>
#include <deque>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <string>
#include <algorithm>
#include <list>
#include <vector>
#include <unordered_set>
#include <unordered_map>
#include <stack>
#include <set>
#include <queue>
#include <map>
/***********MACROS***************/
#define int long long int
#define fri(l,k) for (i=l;i<=k;i++)
#define frj(l,k) for (j=l;j>=k;j--)
#define fij(a,b,l,k) for(i=a;i<=b;i++) for(j=l;j<=k;j++)
#define all(x) x.begin(),x.end()
#define allr(x) x.rbegin(),x.rend()
#define endl "\n"
#define pb push_back
#define _1 first
#define _2 second
#define mxsz 1000000007
#define mxval 1e9 + 7
#define grt [](auto x,auto y){return x>y;}
#define pii pair<int,int>
/*********VARIABLE****************/
using namespace std;
int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
/*********FUNCTIONS**************/
int powom(int a,int b) {
    int result = 1;
    while (b > 0) {
        if (b & 1)
            result = result * a;
        a = a * a;
        b >>= 1;
    }
    return result;
}
/***********MAIN**************/
signed main(){
    ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
    string s;
    cin>>s;
    for(int i=0;i<s.length();i++){
        if((i+1)%2==0&&s[i]=='R'){
            cout<<"No";
            return 0;
        }
        if((i+1)%2!=0&&s[i]=='L'){
            cout<<"No";
            return 0;
        }
    }
    cout<<"Yes";
    return 0;
}
//.........

Compiler output:
a.cc:101:5: error: redefinition of 'long long int i'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |     ^
a.cc:36:5: note: 'long long int i' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |     ^
a.cc:101:7: error: redefinition of 'long long int j'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |       ^
a.cc:36:7: note: 'long long int j' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |       ^
a.cc:101:9: error: redefinition of 'long long int n'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |         ^
a.cc:36:9: note: 'long long int n' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |         ^
a.cc:101:11: error: redefinition of 'long long int m'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |           ^
a.cc:36:11: note: 'long long int m' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |           ^
a.cc:101:13: error: redefinition of 'long long int k'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |             ^
a.cc:36:13: note: 'long long int k' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |             ^
a.cc:101:15: error: redefinition of 'long long int l'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |               ^
a.cc:36:15: note: 'long long int l' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |               ^
a.cc:101:17: error: redefinition of 'long long int q'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                 ^
a.cc:36:17: note: 'long long int q' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                 ^
a.cc:101:19: error: redefinition of 'long long int t'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                   ^
a.cc:36:19: note: 'long long int t' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                   ^
a.cc:101:21: error: redefinition of 'long long int a'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                     ^
a.cc:36:21: note: 'long long int a' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                     ^
a.cc:101:23: error: redefinition of 'long long int b'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                       ^
a.cc:36:23: note: 'long long int b' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                       ^
a.cc:101:25: error: redefinition of 'long long int sum [3]'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                         ^~~
a.cc:36:25: note: 'long long int sum [3]' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                         ^~~
a.cc:101:32: error: redefinition of 'long long int tot [3]'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                                ^~~
a.cc:36:32: note: 'long long int tot [3]' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                                ^~~
a.cc:101:39: error: redefinition of 'long long int cnt [3]'
  101 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                                       ^~~
a.cc:36:39: note: 'long long int cnt [3]' previously declared here
   36 | int i,j,n,m,k,l,q,t,a,b,sum[3],tot[3],cnt[3];
      |                                       ^~~
a.cc:103:5: error: redefinition of 'long long int powom(long long int, long long int)'
  103 | int powom(int a,int b) {
      |     ^~~~~
a.cc:38:5: note: 'long long int powom(long long int, long long int)' previously defined here
   38 | int powom(int a,int b) {
      |     ^~~~~
a.cc:114:8: error: redefinition of 'int main()'
  114 | signed main(){
      |        ^~~~
a.cc:49:8: note: 'int main()' previously defined here
   49 | signed main(){
      |        ^~~~