object Solution {

    def main(args: Array[String]) {
        val sc = new java.util.Scanner (System.in);
        var n = sc.nextInt();
        var A = new Array[Int](n);
        for(A_i <- 0 to n-1) {
           A(A_i) = sc.nextInt();
        }
        val result = calculateDistances(A)
        if(result.size>0)
            print(calculateDistances(A).min)
        else
            print("-1")
    }

    def calculateDistances(data:Array[Int]):Array[Int] = {
        val result = for(i <- 0 until data.size ; j <- i+1 until data.size; if data(i) == data (j)) yield (j-i)
        result.toArray
    }
}