繁华模拟赛 Evensgn的债务

#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<algorithm>
#define ll int
using namespace std;
const int maxn = 1000005;
ll read(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
int v[maxn],sum;
int n,m,a,b,c;
int main(){
    freopen("debt.in","r",stdin);
    freopen("debt.out","w",stdout);
    n = read();
    m = read();
    for(int i = 1;i <= m;i++){
        a = read();
        b = read();
        c = read();
        v[a] -= c;
        v[b] += c;
    }
    for(int i = 1;i <= n;i++){
        if(v[i] >= 0) sum += v[i];
        else sum -= v[i];
    }
    sum >>= 1;
    cout<<sum;
    return 0;
}