#include<stdio.h>
int main(){
    int A, B, N, x, y, z=0;
    scanf("%d%d%d", &A, &B, &N);
    for(x=1; x<=N; x++){

        y = floorfunction(A, B, x);
        if(z>=y)
            continue;
        else
            z = y;

    }

    printf("%d", z);
    return 0;
}
int floorfunction(int A, int B, int x){
    int y;
    y = ((A*x)/B)-(A*(x/B));
    return y;
}