diff --git a/pair_sum.cpp b/pair_sum.cpp
new file mode 100644
index 0000000..840a69d
--- /dev/null
+++ b/pair_sum.cpp
@@ -0,0 +1,85 @@
+#include<bits/stdc++.h>
+#define ll long long
+using namespace std;
+
+int main()
+{
+    ios_base::sync_with_stdio(false);
+    ll t;
+    cin>>t;
+    while(t--)
+    {
+        ll n,q,i,a,b,sum,tmp;
+        cin>>n>>q;
+        vector<ll> v(n-1),ve(n-1,0),vo(n-1,0);
+        ll prev=0;
+        for(i=0;i<n-1;i++)
+        {
+            cin>>v[i];
+            if(i%2==0)
+            {
+                if(i>=2)
+                    ve[i]=v[i]+ve[i-2];
+                else
+                    ve[i]=v[i];
+            }
+            else
+            {
+                if(i>=2)
+                    vo[i]=v[i]+vo[i-2];
+                else
+                    vo[i]=v[i];
+            }
+            v[i]+=prev;
+            prev=v[i]; 
+        }
+        for(i=0;i<q;i++)
+        {
+            cin>>a>>b;
+            a--;
+            b--;
+            if(a>b)
+                swap(a,b);
+        
+            if((b-a)%2==0)
+            {
+                cout<<"UNKNOWN"<<endl;   
+            }
+            else
+            {
+                tmp=0;
+                b--;
+                if(a==0)
+                    sum=v[b];
+                else
+                    sum=v[b]-v[a-1];
+                
+                ll p,q1;
+                p=b-1;
+                if(p%2==0 &&  p>=0)
+                {
+                    p=ve[p];
+                }
+                else if(p>=0)
+                    p=vo[p];
+                else
+                    p=0;
+                
+                if((a-1)%2==0 && a-1>=0)
+                    q1=ve[a-1];
+                else if(a-1>=0)
+                    q1=vo[a-1];
+                else
+                    q1=0;
+                
+                tmp= 2*(p-q1);
+                
+                
+                ll ans=sum-tmp;
+                cout<<ans<<endl;
+                
+            }
+        }
+    }
+    return 0;
+}
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