#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main()
{
    long long int a, b, n;
    scanf("%lld%lld%lld", &a, &b, &n);

    int max = 0, result;

    result = (floor(a*n*1.0/b) - (a*floor(n*1.0/b)));

    printf("%d\n", result);

    return 0;
}
