Compilare: main.cpp: In function 'void precalc()': main.cpp:33:24: warning: iteration 204 invokes undefined behavior [-Waggressive-loop-optimizations] b[i][0]=b[0][i]=0; ~~~~~~~^~ main.cpp:32:14: note: within this loop for(i=1;i<=N;++i) ^ main.cpp:25:24: warning: iteration 204 invokes undefined behavior [-Waggressive-loop-optimizations] a[i][0]=a[0][i]=0; ~~~~~~~^~ main.cpp:24:14: note: within this loop for(i=1;i<=N;++i) ^