#include <stdio.h>
#include <math.h>
typedef unsigned long int uint36_t;
typedef unsigned long long int uint64_t;

int main(void){
	uint32_t a;
	uint64_t b, n, temp;
	scanf("%lu %lu %lu", &a, &b, &n);
	temp = 0;
	for(int i = 1; i <= n; i++){
		if(temp < floor(a*i/b))
		  temp = floor(a*i/b);
	}
	printf("%lu\n", temp);
	return 0;
}