CodeForces 405B Domino Effect【模拟】

Description

Little Chris knows there's no fun in playing dominoes, he thinks it's too random and doesn't require skill. Instead, he decided to play with the dominoes and make a "domino show".

Chris arranges n dominoes in a line, placing each piece vertically upright. In the beginning, he simultaneously pushes some of the dominoes either to the left or to the right. However, somewhere between every two dominoes pushed in the same direction there is at least one domino pushed in the opposite direction.

After each second, each domino that is falling to the left pushes the adjacent domino on the left. Similarly, the dominoes falling to the right push their adjacent dominoes standing on the right. When a vertical domino has dominoes falling on it from both sides, it stays still due to the balance of the forces. The figure shows one possible example of the process.

Given the initial directions Chris has pushed the dominoes, find the number of the dominoes left standing vertically at the end of the process!

Input

The first line contains a single integer n (1 ≤ n ≤ 3000), the number of the dominoes in the line. The next line contains a character string s of length n. The i-th character of the string s_i is equal to

• "L", if the i-th domino has been pushed to the left;
• "R", if the i-th domino has been pushed to the right;
• ".", if the i-th domino has not been pushed.

It is guaranteed that if s_i = s_j = "L" and i < j, then there exists such k that i < k < j and s_k = "R"; if s_i = s_j = "R" and i < j, then there exists such k that i < k < j and s_k = "L".

Output

Output a single integer, the number of the dominoes that remain vertical at the end of the process.

Sample Input

Input

14.L.R...LR..L..

Output

4

Input

5R....

Output

0

Input

1.

Output

1

Hint

The first example case is shown on the figure. The four pieces that remain standing vertically are highlighted with orange.

In the second example case, all pieces fall down since the first piece topples all the other pieces.

In the last example case, a single piece has not been pushed in either direction.

/*    题意：有一堆骨牌,现在告诉你骨牌的初始状态,'.'表示直立,'L'表示向左倒,'R'表示向右倒,问你最后有几个骨牌是直立的    类型：模拟    分析：注意RL这种情况两者不是直立,按照规则模拟就行了*/#include<cstdio>#include<iostream>#include<algorithm>#include<vector>#include<set>#include<cstring>using namespace std;typedef long long ll;const int maxn = 3005;char s[maxn];int res[maxn];int main(){    int n;cin>>n;    scanf("%s",s);    int ans=n;    int f1=0;    int f2=-1;    int sign;    for(int i=0;i<n;i++){        if(s[i]=='L'){            ans-=i-f1+1;            f1=i+1;        }    L1:        if(s[i]=='R'){            sign=0;            f1=i;            for(int j=i+1;j<n;j++){                if(s[j]=='R'){                    ans-=j-i+1;                    i=j;                    f1=i;                    goto L1;                }                if(s[j]=='L'){                    if((j-i+1)%2)ans++;                    ans-=j-i+1;                    i=j;                    f1=i;                    sign=1;                    break;                }            }        }    }    if(!sign)ans-=n-f1;    printf("%d\n",ans);    return 0;}