Cod sursa(job #698479)
#include <cstdio>
int a[25][25], b[25][25];
bool valid(int x, int i){
if(x & (1 << i)) return 1;
return 0;
}
int main(){
freopen("flip.in", "r", stdin);
freopen("flip.out", "w", stdout);
int n, m; scanf("%d%d", &n, &m);
for(int i = 1; i <= n; ++ i) for(int j = 1; j <= m; ++ j) scanf("%d", &b[i][j]);
long long maxi = -999999999;
for(int x = 0 ; x < (1 << m); ++ x){
for(int i = 1; i <= n; ++ i) for(int j = 1; j <= m; ++ j) a[i][j] = b[i][j];
for(int i = 1, k = m; i < (1 << m); (i <<= 1), -- k){
if(valid (x, i)){
for(int j = 1; j <= n; ++ j){
a[j][k] *= -1;
}
}
}
for(int i = 1; i <= n; ++ i){
long long s = 0;
for(int j = 1; j <= m; ++ j)
s += a[i][j];
if(s < 0)
for(int j = 1; j <= m; ++ j)
a[i][j] *= -1;
}
long long s = 0;
for(int i = 1; i <= n; ++ i) for(int j = 1; j <= m; ++ j) s += a[i][j];
if(s > maxi) maxi = s;
}
printf("%lld", maxi);
return 0;
}