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

int floorMax(double t);

int main(void){
    double a,b,n;
    int result = 0;
    int tmp2 = 0;

    scanf("%lf %lf %lf",a,b,n);
    for(double i = 0; i < n; i++){
        result = floorMax((i * a) / b) - floorMax(i / b);
        if(result > tmp2){
            tmp2 = result;
        }
    }
    printf("%d\n",result);

    return(0);
}

int floorMax(double t){
    return((int)t);
}