Problem:
Score : 400 points

Problem Statement

Given are integers A, B, and N.

Find the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-negative integer x not greater than N.

Here floor(t) denotes the greatest integer not greater than the real number t.

Constraints

1 ≤ A ≤ 10^{6}

1 ≤ B ≤ 10^{12}

1 ≤ N ≤ 10^{12}

All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B N

Output

Print the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-negative integer x not greater than N, as an integer.

Sample Input 1

5 7 4

Sample Output 1

2

When x=3, floor(Ax/B)-A×floor(x/B) = floor(15/7) - 5×floor(3/7) = 2. This is the maximum value possible.

Sample Input 2

11 10 9

Sample Output 2

9

Solution in Perl (5.26.1) (judge verdict: Time Limit Exceeded)

my $s = <STDIN>;
chomp $s;
my ($A,$B,$N) = split(/ /,$s);

my $max =0;
for(my $i=1;$i<=$N;$i++){
   my $cal = int(($A*$i)/$B)- $A*int($i/$B);
   if($cal >$max){
     $max = $cal;
   }
}

print "$max";