965D - Single-use Stones - CodeForces Solution

linha = input().split()
 
largura = int(linha[0])
 
l = int(linha[1])
 
rio = input().split()
 
for i in range(len(rio)):
 
    rio[i] = int(rio[i])
 
soma = 0
 
for i in range(l):
 
    soma += rio[i]
 
    i+=1
 
minim = soma
 
for i in range(l, largura-1):
 
    soma = soma - rio[i-l] + rio[i]
 
    minim = min(minim, soma)
 
print(minim)