Probability

Given a input string and ‘n’ random subsequences of that string , what is the probability of realizing original string using these subsequences correctly?Example :Given string = "MISSISSIPPI"Subsequences:1) "MISS"2) "III"3) "MIP"4) "SIS"5) "IS"6…

Given a input string and 'n' random subsequences of that string , what is the probability of realizing original string using these subsequences correctly?Example :

Given string = "MISSISSIPPI"Subsequences:1) "MISS"2) "III"3) "MIP"4) "SIS"5) "IS"6 ) "SP"7) "MP"How many subsequences will be required for optimal probability?Is there any specific structure for subsequences for optimal probability?