玄学CE

#include <bits/stdc++.h>
using namespace std;
#define int long long
int n,m,ans;
int a[2005][2005]={-1};
int st[2005],tot;
char x;
signed main()
{
	scanf("%lld%lld",&n,&m);
	for(int i=1;i<=n;++i)
		for(int j=1;j<=m;a[i][j]=x=='#'?0:a[i][j-1]+1,++j) cin>>x;
	for(int j=1;j<=m;++j,tot=0)
		for(int i=1;i<=n;++i)
		{
			while(tot&&a[i][j]<=a[st[tot]][j]) tot--;
			st[++tot]=i;
			for(int k=tot;k;--k) ans+=(a[st[k]][j]+1)*a[st[k]][j]*((i-st[k-1]+1)*(i-st[k-1])-(i-st[k]+1)*(i-st[k]))>>2;
		}
	printf("%lld",ans);
	return 0;
}