#include <stdio.h>

int f(int A, int B, int x)
{
    return (A * x) / B - A * (x / B);
}

int max(int a, int b) {
    if (a > b)
        return a;
    else
        return b;
}

int main(void)
{
    int A, B, N;
    scanf("%d%d%d", &A, &B, &N);

    int x, res;
    res = 0;
    for (x = 1; x <= N; ++x)
    {
        res = max(res, f(A, B, x));
    }

    printf("%d", res);

    return 0;
}