C++ :

#include<stdio.h>
#include<string.h>

int inc(int x, int n){
	x++; 
	if(x == n) x = 0;
	return x;
}
int del(int x, int n){
	x--;
	if(x < 0) x = n-1;
	return x;
}
int main(){
	//freopen("beads.in","r",stdin);
	//freopen("beads.out","w",stdout);
	int n, ans, i, j;
	char str[400], c;
	int a[400], b[400];
	while(scanf("%d", &n) != EOF){
		scanf("%s", str);
		memset(a, 0, sizeof(a));
		memset(b, 0, sizeof(b));
		for(i = 0; i < n; i++){
			if(str[i] != 'w'){
				c = str[i];
				j = inc(i, n); 
				while(j != i){
					a[i]++;
					if(str[j] != c && str[j] != 'w') break;
					j = inc(j, n);
					
				}
				j = del(i, n);
				c = str[j];
				while(j != i){
					b[i]++;
					j = del(j, n);
					if(c != 'w' && str[j] != c && str[j] != 'w') break;
					if(c == 'w') c = str[j];
				}
			}
		}
		for(i = ans = 0; i < n; i++){
			if(a[i]+b[i] > ans) ans = a[i]+b[i];
		}
		if(ans > n || ans == 0) ans = n;
		printf("%d\n", ans);
	}
    return 0;
}