This ques is solved by DP , and the main idea behind the DP is (considering testers solution — http://codeforces.net/contest/543/submission/11035704)

that either the new coder in the queue will write zero lines of code z[i][j][k] = z[i ^ 1][j][k];

But then the next line just shook me :

z[i][j][k] += z[i][j — 1][k — a[it — 1]];

By which it mean new coder will only take one line as a[it-1] is bugs per line of code .

Now considering a new coder can write lines more than one . Isn't it a bit wrong solution ?