求助！为何CE

#include<bits/stdc++.h>
using namespace std;
#define N 1000005
#define mod 998244353
#define ll long long
#define pii pair<int, int>
int n, a[N][N], fa[N], m, ans;
struct node{int u, v, w;} b[N];
int find(int x){
	if(x==fa[x]) return x;
	else return fa[x]=find(fa[x]);
}
bool cmp(node x, node y){
	return x.w<y.w;
}
main(){
#ifdef GreenMelon
	freopen("", "r", stdin);
	freopen("", "w", stdout);
#endif
	cin>>n;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++){
			cin>>a[i][j];
			if(i!=j) b[++m].u=i, b[m].v=j, b[m].w=a[i][j];
		}
		fa[i]=i;
	}
	sort(b+1, b+m+1, cmp);
	for(int i=1;i<=m;i++){
		if(fa[find(b[i].u)]!=fa[find(b[i].v)]){
			ans+=b[i].w;
			fa[find(b[i].u)]=find(b[i].v);
		}
	}
	cout<<ans;
}

Assembler messages:
Error: value of 000003a355eabefb too large for field of 4 bytes at 0000000000000013
Error: value of 000003a355eabf03 too large for field of 4 bytes at 000000000000001f
Error: value of 000003a355eabf11 too large for field of 4 bytes at 000000000000002d
Error: value of 000003a355eabf9e too large for field of 4 bytes at 00000000000000ba
Error: value of 000003a355eac35f too large for field of 4 bytes at 0000000000000477