#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
typedef long long ll;

int main()
{

    double a,b,n,ans=0,k;
    scanf("%lf %lf %lf",&a,&b,&n);

    if(n>=b)
    {
        b=(b-1)/b;
    }
    else
    {
        b=n/b;
    }
    

    ans=a*b;
    ans=floor(ans);

    printf("%.0f\n",ans);

    return 0;
}