C++中std::cout输出浮点数默认精度是6位有效数字

#include<bits/stdc++.h>
using namespace std;

int a, b;
 
int main()
{
	double res;
	
	scanf("%d%d",&a, &b);
	
	res = (a + b) * 1.0 / 2;
	
	cout << res;

    return 0;
}