Submission #3718603

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Source Code Expand

N=int(input())
table=[]
for i in range(N):
    x,y=map(int,input().split())
    table.append((y,x))
table=sorted(table,reverse=True)
mod=10**9+7
L=[1]*(N+3)
t=1
for i in range(1,N+3):
    t*=i
    t%=mod
    L[i]=t
M=[1]*(N+3)
for i in range(1,N+3):
    M[i]=pow(i,mod-2,mod)
P=[0]*(N+1)
Q=[0]*(N+1)
for i in range(N):
    P[i+1]=P[i]+table[i][1]
    Q[i+1]=Q[i]+table[i][0]*table[i][1]
ans=0
for i in range(1,N-1):
    t=(table[i][0]*(P[N]-P[i])-(Q[N]-Q[i]))%mod
    s=(M[i+1]*M[i+2])%mod
    ans+=(2*L[N]*s*t)%mod
    ans%=mod
print(ans)

Submission Info

Judge Result