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

int main(void){
	int i,d;
	int okMax = 0;
	
	char s[10];
	char week[60];
	
	scanf("%d", &d);
	
	for(i=0;i<d;i++){
		week[i] = 'x';
	}
	
	scanf("%s", s);
	for(i=d;i<(d+7);i++){
		week[i] = s[i-d];
	}
	scanf("%s", s);
	for(i=(d+7);i<(d+14);i++){
		week[i] = s[i-(d+7)];
	}
	for(i=(d+14);i<(d+d+14);i++){
		week[i] = 'x';
		week[i+1] = '\0';
	}
	
	for(i=0;i<(d+14+1);i++){
		int ok=0;
		int j,rest = d;
		char tmp[60]={0};
		strcpy(tmp, week);
		
		for(j=0;j<rest;j++){
			if(tmp[i+j] =='o'){break;}
			tmp[i+j] = 'o';
		}
		for(j=0;;j++){
			if(tmp[j] == 'o'){
				ok++;
			}else{
				if(okMax < ok ){
					okMax = ok;
				}
				ok = 0;
			}
			
			if(tmp[j] == '\0'){break;}
		}
	}
	
	printf("%d\n", okMax);
	
	return 0;
}