1334C - Circle of Monsters - CodeForces Solution

#include<bits/stdc++.h> 
using namespace std ;
#define int long long 
#define endl '\n'
const int maxn = 3e6 + 10 ;
const int mod = 1e9 + 7 ;
int a[maxn], b[maxn] ,c[maxn]; 
void solve() {  
       int n ; cin >> n ;
       int tot = 0 ;
       for(int i =1;i<=n;i++) { 
           cin >> a[i] >> b[i] ;
           if(i > 1) {
           	  c[i] = max(0ll , a[i] - b[i - 1]) ;
           	  tot += c[i] ;
		   }
		   
	   }
	   c[1] = max(0ll ,a[1] - b[n] ) ; 
	   tot += c[1]  ;
	   int mi = a[1] + tot - c[1]; 
	    
	   for(int i =1;i<=n;i++) { 
	       mi = min(mi , a[i] + tot - c[i]) ;
	   }
       cout<<mi<<endl;	
}
/*
     
*/
signed  main () {
   ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int T = 1 ;
         cin >> T ;
     while(T--)solve() ;
        return 0 ;
}