#include <stdio.h>

int main()
{
  long int a,b,n,x,i,max;
  
  scanf("%ld %ld %ld", &a, &b, &n);
  long int ans[n];
  
  x = n;

  i = 0;
  max = 0;
  while (x >= 0) {
    ans[i] = (a*x/b) - a*(x/b);
    i++;
    x--;
  }
  i = 0;
  while (max > ans[i]) {
     i++;
  }

  printf("%ld", ans[i]);
  return(0);
}