N,M,K = map(int, input().split())
inDeg = [0] * (N + 1)
outDeg = [0] * (N + 1)
for _ in range(M):
    a,b = map(int, input().split())
    inDeg[b] += 1
    outDeg[a] += 1
sum_out = 0
n = 0
A = []
for i in range(1,N+1):
    if outDeg[i]>0:
        sum_out += K-inDeg[i]
        n += 1
    else:
        A.append(K-inDeg[i])
if n*(n-1)>=sum_out:
    print(sum_out)
else:
    A = sorted(A)
    cnt = 0
    for i in range(len(A)):
        cnt += A[i]
        if (n+i+1)*(n+i)>=(sum_out+cnt):
            print(sum_out+cnt)
            break