N,M=map(int,input().split())
A=[]
for i in range(M):
    B,C=map(int,input().split())
    A.append((-C,B))
A.sort()

m=dict()
ans=N*(N+1)//2
for c,b in A:
    c=-c
    if c in m:
        c=m[c]
    if c<b:
        continue
    m[b]=c
    ans+=c-b
print(ans)