https://leetcode.com/problems/2-keys-keyboard/description/
解题思路：
- dp[i] = dp[j] + i/j; when i %j == 0
class Solution {
public int minSteps(int n) {
int[] dp = new int[n + 1];
for(int i = 2; i <= n; i++){
dp[i] = i;
for (int j = i - 1; j > 1; j--){
if(i % j == 0){
dp[i] = dp[j] + i / j;
break;
}
}
}
return dp[n];
}
}
