#include <float.h>
#include <inttypes.h>
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <math.h>
#ifdef __cplusplus
#include <bits/stdc++.h>
#endif

int main(void){
	uint32_t a;
	uint64_t b, c;
	scanf("%"SCNu32"%"SCNu64"%"SCNu64, &a, &b, &c);
	uint64_t x=b<=c?b-1:c;
	uint64_t ans = a*x/b - x/b*a;
	printf("%"PRIu64"\n", ans);
}

