#include <stdio.h>

int main() {

	long n;

	while (scanf("%ld",&n) > 0) {
		
		if (n == 1) {
			scanf("%ld",&n);
			printf("1\n");
			continue;
		}

		if (n == 2) {
			scanf("%ld",&n);
			scanf("%ld",&n);
			printf("1\n");
			continue;
		}

		long i;
		long array[n - 1];
		scanf("%ld",&array[0]);
		long lastIn = array[0];
		array[0] = lastIn;

		for (i = 1; i < n; i++) {
			long in;
			scanf("%ld",&in);
			array[i-1] = lastIn-in;
			lastIn = in;
		}

		for(i = n-2; i > 0; i--){
			if(array[i] != array[i-1]) break;
		}

		printf("%ld\n",i+1);
	}

	return 0;
}