cf 25A

#include<stdio.h>

int main()
{
    int n;
    scanf("%d", &n);

    int a[n], i;
    for(i = 0; i < n; i++) scanf("%d", &a[i]);

    int c_even = 0, c_odd = 0, even_idx, odd_idx;
    for(i = 0; i < n; i++)
    {
        if(a[i] % 2 == 0)
        {
            c_even++;
            even_idx = i;
        }
        else
        {
            c_odd++;
            odd_idx = i;
        }
    }
    if(c_even == 1) printf("%d\n", even_idx + 1);
    else if(c_odd == 1) printf("%d\n", odd_idx + 1);
}