give string s return number homogenous substring s since answer large return modulo 109 7a string homogenous character stre sameA substre contiguous sequence character string Example 1input s abbcccaaoutput 13explanation the homogenous substring list belowa appear 3 timesaa appear 1 timeb appear 2 timesbb appear 1 timec appear 3 timescc appear 2 timesccc appear 1 time3 1 2 1 3 2 1 13example 2input s xyOutput 2explanation the homogenous substring x yexample 3input s zzzzzOutput 15 Constraints1 slength 105s consist lowercase letter