Uva 10013 - Super long sums

/// Accepted

/// Header file begin
#include<iostream>
#include<cstdio>
#include<cstring>
#include<map>
#include<string>
#include<vector>
#include<cmath>
#include<cctype>
#include<sstream>
#include<set>
#include<list>
#include<stack>
#include<utility>
#include<queue>
#include<algorithm>
#include<cstdlib>
/// End
//..........
/// Macro
#define sf scanf
#define pf printf
#define lp1(i,n) for(i=0;i<n;i++)
#define lp2(i,n) for(i=1;i<=n;i++)
#define mem(c,v) memset(c,v,sizeof(c))
#define cp(a) cout<<" "<<a<<" "
#define nl puts("")
#define sq(x) ((x)*(x))
#define all(x) x.begin(),x.end()
#define reall(x) x.rbegin(),x.rend()
#define sz size()
#define gc getchar()
#define pb push_back
#define freader freopen("input.txt","r",stdin)
/// End.........

/// Size
#define mx7 20000100
#define mx6 1500000
#define mx5 100005
#define mx4 1000100
#define inf 1<<30                                           //infinity value
#define eps 1e-9
#define mx (65540)
#define mod 1000000007
#define pi acos(-1.0)

/// Macros for Graph

#define white 1
#define gray 2
#define black 3
#define nil 0

using namespace std;
/***************/

/// typedef

typedef long long LL;
typedef long L;
typedef unsigned long long ull;
typedef unsigned long ul;
typedef unsigned int ui;
typedef pair<int, int> pii;
typedef vector<int>vi;
typedef vector<long long> vll;
typedef vector<long>vl;
typedef vector<char>vch;
typedef vector<string>vs;
typedef map<int,int>mpii;
typedef map<int,bool>mpbi;
typedef map<long,bool>mpbl;
typedef map<long long,bool>mpbll;
typedef map<char,int>mpci;
typedef map<char,bool>mpbc;
typedef map<string,int>mpsi;
typedef map<long long,long long>mpll;

/// template

template<class T> T gcd(T a, T b ) {return b<=0?a:gcd(b,a%b);}
template<class T> T large(T a, T b ) {return a>b?a:b;}
template<class T> T small(T a, T b ) {return a<b?a:b;}
template<class T> T diffrnce(T a, T b) {return a-b<0?b-a:a-b;}

/// macros for seieve

#define setbit(n) (prime[n>>6]|=((1<<(n>>1))&31))
#define checkbit(n) (prime[n>>6]&((1<<(n>>1))&31))

LL arr[mx4+6],brr[mx4+6],ans[mx4+6];

int main()
{
    L test;
    sf("%ld",&test);

    for(L k=0;k<test;k++)
    {
        if(k>0)nl;
        LL n,i;
        sf("%lld",&n);

        for(i=0;i<n;i++)
        {
            LL x,y;
            sf("%lld %lld",&x,&y);
            arr[i]=x;
            brr[i]=y;
        }

        LL carry=0,len=0;

        for(i=n-1;i>=0;i--)
        {
            carry += arr[i]+brr[i];
            ans[len++]=carry%10;
            carry=carry/10;
        }

        //for(i=0;i<n;i++)cout<<ans[i] << " ";
        for(i=len-1;i>=0;i--)
        {
            pf("%lld",ans[i]);
        }

        nl;
    }

    return 0;
}