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  1. Practice
  2. Algorithms
  3. Strings
  4. Mars Exploration

Mars Exploration

A space explorer's ship crashed on Mars! They send a series of SOS messages to Earth for help.

Letters in some of the SOS messages are altered by cosmic radiation during transmission. Given the signal received by Earth as a string, , determine how many letters of the SOS message have been changed by radiation.

Example

The original message was SOSSOS. Two of the message's characters were changed in transit.

Function Description

Complete the marsExploration function in the editor below.

marsExploration has the following parameter(s):

  • string s: the string as received on Earth

Returns

  • int: the number of letters changed during transmission

Input Format

There is one line of input: a single string, .

Constraints

  • will contain only uppercase English letters, ascii[A-Z].

Sample Input 0

SOSSPSSQSSOR

Sample Output 0

3

Explanation 0

= SOSSPSSQSSOR, and signal length . They sent SOS messages (i.e.: ).

Expected signal: SOSSOSSOSSOS
Recieved signal: SOSSPSSQSSOR
Difference:          X  X   X

Sample Input 1

SOSSOT

Sample Output 1

1

Explanation 1

= SOSSOT, and signal length . They sent SOS messages (i.e.: ).

Expected Signal: SOSSOS     
Received Signal: SOSSOT
Difference:           X

Sample Input 2

SOSSOSSOS

Sample Output 2

0

Explanation 2

Since no character is altered, return 0.