Compilare: main.cpp: In function 'int main()': main.cpp:21:29: warning: left operand of comma operator has no effect [-Wunused-value] for(int ii=i+i,jj=j+j;ii<=m,jj<=n;ii+=i,jj+=j) ~~^~~ main.cpp:34:3: warning: this 'if' clause does not guard... [-Wmisleading-indentation] if(a==0) a=1; if(b==0) b=1; if(c==0) c=1; if(d==0) d=1; ^~ main.cpp:34:17: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if' if(a==0) a=1; if(b==0) b=1; if(c==0) c=1; if(d==0) d=1; ^~