1 #include<cstdio> 2 #include<cstring> 3 #include<vector> 4 #include<algorithm> 5 #define CLR(a,b) memset((a),(b),sizeof((a))) 6 using namespace std; 7 const int N = 501; 8 int dp[N][N]; 9 int main(){10     int n, m, i, j, k, s, ans, x;11     scanf("%d%d", &m, &n);12     CLR(dp, 0);13     for(i = 1; i <= n; ++i){14         for(j = 1; j <= m; ++j){15             scanf("%d", &x);16             dp[i][j] = x + dp[i-1][j];17         }18     }19     ans = 0;20     for(i = 1; i <= n; ++i){21         for(j = i; j <= n; ++j){22             s = 0;23             for(k = 1; k <= m; ++k){24                 x = dp[j][k] - dp[i-1][k];25                 if(s > 0)26                     s += x;27                 else28                     s = x;29                 ans = max(ans, s);30             }31         }32     }33     printf("%d\n", ans);34     return 0;35 }