H,W,K=map(int,input().split())
MAP=[[0]*W for _ in range(H)]
for _ in range(K):
    x,y,v=map(int,input().split())
    x-=1
    y-=1
    MAP[y][x]=v

sousa=[[0]*W for _ in range(H)]
for i in range(H):
    for j in range(W):
        for y in range(H):
            for x in range(W):
                if not(x+y>=i+j and x-y>=i-j):
                    continue
                sousa[i][j]+=MAP[y][x]

ans=0
for i in range(H):
    ans+=sum(sousa[i])
print(ans)