The Problem is Three is Crowd. Link is http://www.codechef.com/problems/CROWD My code is

include <iostream>

include <iomanip>

define ll unsigned long long

define mod 1000000007

using namespace std;

int main() {

ll t; cin>>t;

ll x,y,z,i;

while(t--)
{
        z=0;
        cin>>x;
        if(x<3)cout<<"0\n";
        else{
        y=x-2;   y=y%mod;
        z=(y*(y+1));   z=z/2;
        cout<<z%mod<<"\n";
        }
}

return 0;

}

My Logic is that : Suppose there are 6 Houses First : (1,2,3) , (2,3,4) , (3,4,5) , (4,5,6) (i.e total=4 (6-2)) Second : (1,2,3,4) , (2,3,4,5) , (3,4,5,6) (i.e total=4+3) Third : (1,2,3,4,5) , (2,3,4,5,6) (i.e total=4+3+2) Fourth : (1,2,3,4,5,6) (i.e total=4+3+2+1)

Indirectly ,the answer is sum of no's from 1 to (no of Houses - 2) if no of houses>=3 else answer=0 Here it is 1 to 4, so answer is 1+2+3+4=10

For the Problem test cases : Input 3 : ans=1 4 : ans=1+2=3

But getting Wrong Answer ..Pls Help