class UnionFind:
    def __init__(self, n):
        self.par = [-1]*n
        self.rank = [0]*n

    def Find(self, x):
        if self.par[x] < 0:
            return x
        else:
            self.par[x] = self.Find(self.par[x])
            return self.par[x]

    def Unite(self, x, y):
        x = self.Find(x)
        y = self.Find(y)

        if x != y:
            if self.rank[x] < self.rank[y]:
                self.par[y] += self.par[x]
                self.par[x] = y
            else:
                self.par[x] += self.par[y]
                self.par[y] = x
                if self.rank[x] == self.rank[y]:
                    self.rank[x] += 1

    def Same(self, x, y):
        return self.Find(x) == self.Find(y)

    def Size(self, x):
        return -self.par[self.Find(x)]

n, m = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
X = []
for a in A:
    X.append((a, 0))
for b in B:
    X.append((b, 1))
X.sort(key=lambda x: x[0])
E = []
for i, (x, t) in enumerate(X):
    if t == 0:
        E.append((0, i, n+m))
for i in range(len(X)-1):
    d = X[i+1][0]-X[i][0]
    E.append((d, i, i+1))
E.sort(key=lambda x: x[0])
ans = 0
uf = UnionFind(n+m+1)
for d, u, v in E:
    if uf.Same(u, v):
        continue
    else:
        ans += d
        uf.Unite(u, v)
print(ans)