#include <stdio.h>

int main(void)
{
    int c;
    unsigned long int a, b, n;
    scanf("%lu %lu %lu", &a, &b, &n);


    if(n <= b){
        printf("%lu", (a*n)/b);
    }else
    {
        printf("%lu", (a * n) / b - a*(int)(n/b));
    }
    


    return 0;
}