I have an issue in c++ code, in this test
vector numbers { 1,100,50,-51,1,1 };

In my IDE output is: 1, but in code wars i have output -1.

This is my code

int find_even_index (const std::vector numbers) {
int sum_r = 0;
int sum_l = 0;
for(int i = 0; i < numbers.size(); i++){
for (int l = 0; l < i; l++) {
sum_l += numbers[l];
}
for (long int r = numbers.size(); r > i; r--) {
sum_r += numbers[r];
}
if (sum_l == sum_r) {
return i;
} else sum_l = 0; sum_r = 0;
}
return -1;
}

Please help me find out what is the problem