Sgu/146

模拟题 注意四舍五入即可

#include<cstdio>
#include<cmath>
 
typedef long long LL;
 
const int E=10000;
LL len,v,t,sum;
double answer,l;
int n;
 
int main()
{
	freopen("146.in","r",stdin);
	freopen("146.out","w",stdout);
	int i;
	scanf("%lf %d",&l,&n);
	len=round(l*E);
	for(i=1;i<=n;++i)
	{
		scanf("%lld %lld",&v,&t);
		sum+=v*t*E;
		sum%=len;
	}
	answer=(double)sum;
	answer/=E;
	if(l-answer<answer)answer=l-answer;
	printf("%.4lf",answer);
}