#include <iostream>
#include <string>
using namespace std;
int pivotIndex(int nums[])
{
int sum = 0;
for (int i = 0; i < 7; i++)
{
sum += nums[i];
}
int leftSum = 0;
int rightSum = sum;
int pastPivotNum = 0;
for (int i = 0; i < 7; i++)
{
int num = nums[i];
rightSum = rightSum - num;
leftSum = leftSum + pastPivotNum;
if (leftSum == rightSum)
{
return i;
}
pastPivotNum = num;
}
return -1;
}
int main()
{
int a[] = {1, 8, 2, 9, 2, 3, 6};
cout << pivotIndex(a) << endl;
return 0;
}