#include <stdio.h>
int main()
{
int T,n,m,i, check = 0;
double sum = 0;
scanf("%d %d",&m,&n);
sum = (double)m / (double)n;
if(n < 0) printf("0");
else if(n > m) printf("0");
else if(0 <= n && n <= m)
{
if(n == 0 && m ==0){ printf("0"); return 0;}
m--;
n--;
while(n > 0)
{
if(check == 0)
{
sum = sum * (double)m; // 컴비네이션 쓰면 값이 커져서 분할시켰다.
m--;
check = 1;
}
else if(check == 1)
{
sum = sum / (double)n;
n--;
check = 0;
}
}
printf("%.f",sum);
}
return 0;
}
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