for (int i = 2; i<=n; i++ ) 
		{	
				int	x = i%3 , y = (i-1)%3 , z = (i-2)%3; 
				for (int	 j = 0; j < n-i+1; j++ ) 
				{	
						if ( s[j] == s[j+i-1] ) dp[x][j] = dp[z][j+1]; 
						else dp[x][j] = dp[z][j+1] + 2; 
						dp[x][j] = min( dp[x][j] , dp[y][j] + 1 ); 
						dp[x][j] = min( dp[x][j] , dp[y][j+1] + 1 );
				}
		}