fayed

#include<stdio.h>
int main () {
int a,b=0,c=0,d,i;
scanf("%d",&a);
for(i=2;i<=a;i++){
    if(i%2==0)
    {c=c+i;}
    if(i%2!=0 )
    {b=b+i;
    }
    }
    d=c-b;
    d=d-1;
printf("%d",d);
return 0;
}