#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);

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

    temp = A*N/B - N/B*A;

    printf("%lld",temp);

    return 0;
}