int rsq(int x, int y){
     int y1;
     int x1 = x;
     int sumaux = 0;
     for (; x1; x1-= x1&(-x1)){
        y1 = y;
        for(; y1; y1 -= y1&(-y1)){
            sumaux += matrix[x1][y1];
        }
     }
     return sumaux;
}

int rsq(int x, int y, int x2, int y2){
     int y1;
     int x1 = x2;
     int sumaux = 0;
     for (; x1; x1-= x1&(-x1)){
        y1 = y;
        for(; y1; y1 -= y1&(-y1)){
            sumaux += matrix[x1][y1];
        }
     }
     return sumaux - ((x == 1 ||y == 1) ? 0 : rsq(x-1, y-1));
}