/in/foo.cc: In function 'int main()':
/in/foo.cc:25:14: warning: iteration 99 invokes undefined behavior [-Waggressive-loop-optimizations]
     gra[i][j]=min(gra[i][j],gra[i][k]+gra[k][j]);
     ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/in/foo.cc:24:17: note: within this loop
    for(int j=1;j<=n;j++)
                ~^~~