function minimumDistances(a) {
    let min;
    const findOtherIndex = index => {
    	for (let i = index + 1; i < a.length; i++) {
      	if (a[i] === a[index]) {
        	return i;
        }
      }
      return null;
    }
    for(let i = 0; i < a.length; i++) {
        if (findOtherIndex(i)) {
        	if (!min) {
        		min = Math.abs(i - findOtherIndex(i))
        	} else {
          	if (Math.abs(i - findOtherIndex(i)) < min) {
            	min = Math.abs(i - findOtherIndex(i))
            }
          }
        }
    }
    return min || -1;
}