CodeForces - 560C Gerald's Hexagon

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<ctype.h>
using namespace std;
int a[10];
int main() {
int sum = 0;
for (int i = 0; i < 6; i++)
scanf("%d", &a[i]);
sum = a[0] + a[1] + a[2];
sum = sum * sum - a[0] * a[0] - a[2] * a[2] - a[4] * a[4];
printf("%d\n", sum);

return 0;
}