Help needed to solve Training - INOI 2017

Problem Link: https://www.codechef.com/INOIPRAC/problems/TINOI17B
Solution Link: https://www.codechef.com/viewsolution/27481977

The strategy used (dynamic programming):
dp[i][numberOfTrains]=maxstrength;

dp[i][0]=dp[i-1][0]+s[0]*e[i];
dp[i][j]=max(dp[i-1][j]+s[j]*e[i],dp[i-1][j-1])
dp[i][any j greater than i]=0

answer is max from dp[n-1][0] to dp[n-1][n]

Here, s[i]=strength after i training
e[i]=experience at i city

You provided the problem, solution and the approach. So what help so you need?