Password Permutation/Combination Problem So here's the problem:
At a certain company, passwords must be from 3-5 symbols long and composed of the 26 letters of the alphabet, the ten digits 0-9, and the 14 symbols !,@,#,$,%,ˆ,&,*,(,),-,+,{, and }.
a. How many passwords are possible if repetition of symbols is allowed? b. How many passwords contain no repeated symbols? c. How many passwords have at least one repeated symbols?
I got 50^5 (312,500,000) for A and 50! for B, and I know the formula to figure out C is 
|at least one|=|all|−|none|
but if I do A - B, I end up with a negative number, which I know isn't correct. What am I doing wrong?

Number of passwords with (possible) symbol-repetition:
$(50^3)+(50^4)+(50^5)=318875000$

Number of passwords without any symbol-repetition:
$(50\cdot49\cdot48)+(50\cdot49\cdot48\cdot47)+(50\cdot49\cdot48\cdot47\cdot46)=259896000$

Number of passwords with at least one symbol-repetition:
$318875000-259896000=58979000$
