Codeforces 455E - Function

Problem Statement:
http://codeforces.com/contest/455/problem/E

Summary:
Given a function f(i, j) = min (f(i-1, j), f(i-1, j-1)) + a[j], where f(1, j) = a[j], and m queries (m <= 10^5) in the form (i, j), compute f(i, j) of each queries.