为什么输入30 40 50，我的结果是6663.495？？

#include <bits/stdc++.h>
#define int long long
#define iostream() ios::sync_with_stdio(false),cin.tie(NULL),cout.tie(NULL);
#define PI 3.1415926535
using namespace std;
const int maxn = 1e6+7;
const int MAXN = maxn / 2;
signed main()
{
    iostream();
    int a,b,c;
    cin >> a >> b >> c;
    double g = ((a * (b + c)) + (b * c) + ((PI * c * c) / 4.0));
    printf("%.3lf",g);
 	return 0;
}