Arithmetic Sequence (Easy)

Arithmetic Sequence is a sequence of numbers where the difference between two consecutive numbers ar…

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#include<iostream>
using namespace std;
int main()
{
	int N,M,sum,sub,x;
	scanf("%d",&N);
	sum=N*(N+1)/2;
	scanf("%d",&M);
	while(M--) 
	{
	    /* code */
	    scanf("%d",&x);
	    sub+=x;
	    //M--;
	}
	printf("%d\n",sum-sub);
	return 0;
}

My code gives correct output but when i submitted it shows wrong answer. Where is the problem?

you should use
sub=0 in 5th line
also while(m--)