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14929. 귀찮아 (SIB) - Useful Blog

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14929. 귀찮아 (SIB)

written by Useful·BOJ 14929


c
#include  <bits/stdc++.h>

using namespace std;

int main(){
    cin.tie(NULL);
    cout.tie(NULL);
    ios_base::sync_with_stdio(false);

    int N;
    cin >>

N

;

vector

<

long

long

>

arr

;

for

(

int

i

=

0

;

i

<

N

;

i

++

)

{

long

long

input

;

cin

>>

input

;

arr

.

push_back

(

input

)

;

if

(

i

>

0

)

{

arr

[

i

]

+=

arr

[

i

-

1

]

;

}

}

long

long

ans

=

0

;

for

(

int

i

=

0

;

i

<

N

;

i

++

)

{

ans

+=

(

arr

[

N

-

1

]

-

arr

[

i

]

)

*

(

arr

[

i

]

-

(

i

>

0

?

arr

[

i

-

1

]

:

0

)

)

;

}

cout

<<

ans

<<

"\n"

;

return

0

;

}