C++ :

#include<bits/stdc++.h>
using namespace std;
int n,m,A[110000],s[110000],a,b;
int main()
{
//	freopen("chicken0.in","r",stdin);
//	freopen("chicken0.out","w",stdout);
	scanf("%d%d",&n,&m);
	for(int i=1;i<=n;i++)
	{
		scanf("%d",&A[i]);
		s[i]=s[i-1]+A[i];
	}
	for(int i=1;i<=m;i++)
	{
		scanf("%d%d",&a,&b);
		if(a>b) swap(a,b);
		printf("%d\n",s[b]-s[a-1]);
	}
	return 0;
}