Maximum Sum

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <fstream>
#include <iostream>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#include <iomanip>
using namespace std;
/*** typedef ***/
#define MEMSET_INF 127
#define MEMSET_HALF_INF 63
#define stream istringstream
#define rep(i,n) for(__typeof(n) i=0; i<(n); i++)
#define repl(i,n) for(__typeof(n) i=1; i<=(n); i++)
#define FOR(i,a,b) for(__typeof(b) i=(a); i<=(b); i++)
#define INF (1<<30)
#define PI acos(-1.0)
#define pb push_back
#define ppb pop_back
#define all(x) x.begin(),x.end()
#define mem(x,y) memset(x,y,sizeof(x))
#define memsp(x) mem(x,MEMSET_INF)
#define memdp(x) mem(x,-1)
#define memca(x) mem(x,0)
#define eps 1e-9
#define pii pair<int,int>
#define pmp make_pair
#define ft first
#define sd second
#define vi vector<int>
#define vpii vector<pii>
#define si set<int>
#define msi map<string , int >
#define mis map<int , string >
typedef long long i64;
typedef unsigned long long ui64;
/** function **/
#define SDi(x) sf("%d",&x)
#define SDl(x) sf("%lld",&x)
#define SDs(x) sf("%s",x)
#define SD2(x,y) sf("%d%d",&x,&y)
#define SD3(x,y,z) sf("%d%d%d",&x,&y,&z)
#define pf printf
#define sf scanf
#define READ(f) freopen(f, "r", stdin)

#define Max 100
#define INT_MIN -INFFF
int main() {
    READ("in.txt");
    int row, col;
    int M[Max + 10][Max + 10];
    SD2(row, col);

    rep(i, row) rep(j, col) {
        SDi(M[i][j]);
        if(i > 0) M[i][j] += M[i - 1][j];
        if(j > 0) M[i][j] += M[i][j - 1];
        if(i > 0 && j > 0) M[i][j] -= M[i - 1][j - 1]; // inclusion-exclusion principle
    }

    int maxSum = INT_MIN, sum;
    rep(i, row) rep(j, col) FOR(k, i, row - 1) FOR(l, j, col - 1) {
        sum = M[k][l];
        if(i > 0) sum -= M[i - 1][l];
        if(j > 0) sum -= M[k][j - 1];
        if(i > 0 && j > 0) sum += M[i - 1][j - 1]; // inclusion-exclusion principle
        maxSum = max(maxSum, sum);
    }
    pf("%d\n", maxSum);
    return 0;
}