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183. Painting the balls

time limit per test: 0.25 sec.
memory limit per test: 4096 KB
input: standard input
output: standard output

Petya puts the N white balls in a line and now he wants to paint some of them in black, so that at least two black balls could be found among any M successive balls. Petya knows that he needs Ci milliliters of dye exactly to paint the i-th ball. Your task is to find out for Petya the minimum amount of dye he will need to paint the balls.

The first line contains two integer numbers N and M (2<=N<=10000, 2<=M<=100, M<=N). The second line contains N integer numbers C1, C2, ..., CN (1<=Ci<=10000).

Output only one integer number - the minimum amount of dye Petya will need (in milliliters).

Sample test(s)

6 3
1 5 6 2 1 3


Example note: 1, 2, 4, 5 balls must be painted.

Author:Andrew V. Lazarev
Resource:ACM International Collegiate Programming Contest 2003-2004
North-Eastern European Region, Southern Subregion
Date:2003 October, 9