/*
 * FileName:     D_fix
 * CreatedDate:  2020-05-02 22:31:53 +0900
 * LastModified: 2020-05-02 22:33:40 +0900
 */

#include <stdio.h>

int main(void){
    long long int a,b,n;
    scanf("%lld %lld %lld",&a,&b,&n);
    printf("%lld\n",(a*n-a*n%b)/b-a*(n-n%b)/b);
    return 0;
}
