const int N = 1024;


void trsm(int n, float A[][N], float B[][N]) {
  int i, j, k;

  k = 0;
  while (k < n) {
    i = 0;
    while (i < n) {
      B[i][k] = B[i][k] / A[i][i];
      j = i + 1;
      while (j < n) {
        B[j][k] = B[j][k] - A[j][i] * B[i][k];
        j = j + 1;
      }
      i = i + 1;
    }
    k = k + 1;
  }
}

float A[N][N];
float B[N][N];
float C[N][N];

int main() {
  int n = getint();
  int i, j, k;

  i = 0;
  j = 0;
  while (i < n) {
    j = 0;
    while (j < n) {
      A[i][j] = getfloat();
      j = j + 1;
    }
    i = i + 1;
  }
  i = 0;
  j = 0;
  while (i < n) {
    j = 0;
    while (j < n) {
      C[i][j] = getfloat();
      j = j + 1;
    }
    i = i + 1;
  }

  starttime();
  k = 0;
  while (k < 5) {
    i = 0;
    while (i < n) {
      j = 0;
      while (j < n) {
        B[i][j] = C[i][j];
        j = j + 1;
      }
      i = i + 1;
    }
    trsm(n, A, B);
    k = k + 1;
  }
  stoptime();

  float ans = 0;
  i = 0;
  while (i < n) {
    j = 0;
    while (j < n) {
      ans = ans + B[i][j];
      j = j + 1;
    }
    i = i + 1;
  }

  putfloat(ans);
  putch(10);

  return 0;
}