the agreed answer:
        0     1    -3     2    -4
        3     0    -4     1    -1
        7     4     0     5     3
        2    -1    -5     0    -2
        8     5     1     6     0

SLOW-APSP            agrees with |V| x Bellman-Ford: YES
repeated squaring    agrees with |V| x Bellman-Ford: YES
Floyd-Warshall       agrees with |V| x Bellman-Ford: YES
Johnson              agrees with |V| x Bellman-Ford: YES

all five methods agree: YES
