Managing Event

You have a string s1 s2………sn and a character r and you want to make all characters of the string equal to r using the minimum number of operations. In one operation you can choose a number z (1≤z≤n) and for every position i, where i is not divisible by z, replace si with r. Find the minimum number of operations required to make all the characters equal to r and the z-s that you should use in you