int main()
{
    long long int a,b,n;
    scanf("%lld %lld %lld",&a,&b,&n);
    if(a*b>0) printf("%lld",(a*n/b)-(a*(n/b)));
    if(a*b<0) printf("0");
    //if(a*b<0&&n>b) printf("%d",(a*(n/b))-(a*n/b));
}
