#include<stdio.h>

int main(void){
    /*int N,M,Q;

    scanf("%d %d %d",&N,&M,&Q);

    int a[Q],b[Q],c[Q],d[Q]; */

    long long int A,B,N,x,n=0,temp;

    scanf("%lld %lld %lld",&A,&B,&N);

    if(B>A){
    for(x=0;x<=N;x++){
        temp = A*x/B - x/B*A;
        //printf("%lld\n",temp);
        //if(temp>n) n = temp;
        if(x==B-1) n = temp;
    }
    printf("%lld",n);
    }

    if(A>=B) printf("%lld",A*N/B - N/B*A);
    

    return 0;
}