public String determBacktrack(int start,int end){
		String seq="";
		int max = this.maxBasepairs[start][end];
		if(start == end)
			return ".";
		if(start > end)
			return "";
		if(isValidPair(start,end) && this.maxBasepairs[start+1][end-1]+1 == max)
			return "("+determBacktrack(start+1,end-1)+")";
		if(this.maxBasepairs[start][end-1]==max)
			return determBacktrack(start,end-1)+".";
		if(this.maxBasepairs[start+1][end]==max)
			return "."+determBacktrack(start+1,end);
		for(int k = start +1;k<end;k++){
			if(this.maxBasepairs[start][k]+this.maxBasepairs[k+1][end]==max)
				return determBacktrack(start,k)+determBacktrack(k+1,end);
		}
		return seq;
	}