warshall code

#include <iostream>
#include <fstream>
using namespace std;
int L[100][100], a[100][100], n;
bool viz[100];
void citire()
{
    ifstream f("graf.in");
    f>>n;
    for (int i=1; i<=n; ++i)
        for(int j=1; j<=n; j++)
            f>>a[i][j];
}
int main()
{
    int i, j, k;
    citire();
    for (int i=1; i<=n; ++i)
        for(int j=1; j<=n; j++)
            L[i][j]=a[i][j];
    for(k=1; k<=n; k++)
        for (int i=1; i<=n; ++i)
            for(int j=1; j<=n; j++)
                if(k!=i&& k!=j&&i!=j&&L[i][j]==0)
                    L[i][j]=L[i][k]*L[k][j];
    for (int i=1; i<=n; ++i)
    {
        for(int j=1; j<=n; j++)
            cout<<L[i][j]<<" ";
        cout<<endl;
    }
}
/*
graf.in
6
0 1 0 1 0 0
1 0 0 0 0 0
0 0 0 1 0 0
1 0 1 0 1 0
0 0 0 1 0 1
0 0 0 0 1 0
*/