ICPC-无限路之城

https://ac.nowcoder.com/acm/contest/321/C

题解：假设已建的边在最少城市之间

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=10000;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
ll t,n,m,k,q;

int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    while(~scanf("%lld",&t))
    while(t--){
        scanf("%lld%lld",&n,&m);
        if(n*(n-1)/2>=m)
            cout << n*(n-1)/2-m << endl;
        else
            cout << 0 << endl;
    }
    //cout << "Hello world!" << endl;
    return 0;
}