#include <stdio.h>
#include <string.h>
#define MAX(a,b) ((a)>(b)?(a):(b))
 
int main(void) {
	int k, dp[1005][1005], i, j, xlen, ylen, c;
	char x[1005], y[1005];
 
	while(1){
		scanf("%d", &k);
		if(k==0)
			break;
		scanf("%s%s", x, y);
 
		xlen = strlen(x);
		ylen = strlen(y);
 
		for(i=0; i<=xlen; i++){
			for(j=0; j<=ylen; j++){
				dp[i][j] = 0;
				if(i==0 || j==0)
					continue;
 
				c = 1;
				while(i-c>=0 && j-c>=0 && x[i-c]==y[j-c]){
					if(c>=k)
						dp[i][j] = MAX(dp[i][j], c+dp[i-c][j-c]);
					c++;
				}
				dp[i][j] = MAX(dp[i][j], dp[i-1][j]);
				dp[i][j] = MAX(dp[i][j], dp[i][j-1]);
			}
		}
 
		printf("%d\n", dp[xlen][ylen]);
	}
 
	return 0;
}
 

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3
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xxxxxxxlovely
1
lovxxelyxxxxx
xxxxxxxlovely
3
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xxxlovelyxxxxxxx
4
lovxxxelyxxx
xxxxxxlovely
0