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


int main(void) {

	long long int valueA, valueB, valueN;

	char str[1000];

	fgets(str,sizeof(str),stdin);

	sscanf(str,"%lld %lld %lld",&valueA,&valueB,&valueN);

	long long int max = 0;

	long long int tempResult = 0;

	for (int x = 1; x <= valueN; x++) {

		tempResult = floor((x * valueA) / valueB) - floor(x/valueB);

		max = (max < tempResult) ? tempResult : max;

	}

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

	return 0;

}
