Compilare: main.cpp: In function 'int main()': main.cpp:17:3: warning: this 'for' clause does not guard... [-Wmisleading-indentation] for(i=2;i*i<=nmax;i++) ^~~ main.cpp:21:5: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for' int ok=1; ^~~ main.cpp:11:15: warning: unused variable 'r' [-Wunused-variable] long long int r; ^ main.cpp:12:22: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&n); ^ main.cpp:24:14: warning: iteration 2000005 invokes undefined behavior [-Waggressive-loop-optimizations] if(v[i]==1) ~~~^ main.cpp:22:19: note: within this loop for(i=2;i<=nmax && ok==1;i++) ~~~~~~~~^~~~~~~~ main.cpp:15:11: warning: iteration 2000005 invokes undefined behavior [-Waggressive-loop-optimizations] v[i]=1; ~~~~^~ main.cpp:13:12: note: within this loop for(i=2;i<=nmax;i++) ^