class Solution:
    # @return a string
    def convert(self, s, nRows):
        row_len = 2 * nRows - 2
        string = ["" for _ in range(nRows)]
        
        if nRows <= 2:
          for i in range(len(s)):
        	string[i % nRows] += s[i]
        else:
          for i in range(len(s)):
        	res = i % row_len
        	if res in range(nRows, row_len):
        	   string[row_len - res] += s[i]
        	else:
        	   string[res] += s[i]

        output = ""
        for i in range(nRows):
        	output += string[i]

        return output