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

int main()
{
	double B,N,n,C;
	int A,max = 0;

	scanf("%d %lf %lf",&A,&B,&N);

	if (N < B){
		max = floor(A * N / B) - A * floor(N / B);
	}else{
		for (double x = B - 1;x <= N;x += B){
			C = floor(A * x / B) - A * floor(x / B);
			if (max < C) max = C;
		}
	}

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

	return 0;
}
