#include <stdio.h>



int *pX = nullptr;
int N = 0;


int GetDiff ( int idx1 , int idx2 );


int main ( void ) {


	scanf ( "%d" , &N );


	pX = new int [ N ];
	int diff , diffbuf;

	for ( int i = 0; i < N; i++ ) {
		scanf ( "%d" , pX + i );
	}


	for ( int i = 0; i < ( N - 1 ); i++ ) {
		//printf ( "Call\n" );
		if ( i == 0 ) {

			diff = GetDiff ( i , i + 1 );

		} else {
			diffbuf = GetDiff ( i , i + 1 );
			if ( diffbuf != -1 ) {
				if ( diffbuf < diff ) diff = diffbuf;
			}
		}
		if ( diff == 1 )break;
	}
	delete []pX;

	if ( diff == -1 ) diff = 0;
	printf ( "%d\n" , diff );
	return 0;
}

int GetDiff ( int idx1 , int idx2 ) {
	//printf ( "%d %d\n" , idx1 , idx2 );
	bool bEnableCurrent = false;
	int Current;

	if ( *( pX + idx1 ) != *( pX + idx2 ) ) {
		bEnableCurrent = true;
		Current = *( pX + idx1 ) - *( pX + idx2 );
		if ( Current < 0 ) Current *= -1;
		if ( Current == 1 ) return Current;
	}

	int diff= -1 , idxnext;

	idxnext = idx2 + 1;
	diff = ( idxnext < N ) ? GetDiff ( idx1 , idxnext ) : -1;

	if ( diff == 1 )return diff;

	if ( bEnableCurrent ) {
		if (diff != -1 )return ( Current < diff ) ? Current : diff;
		return Current;
	}
	return diff;

}