Compilare: main.cpp: In function 'int prep()': main.cpp:196:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(unsigned long long j=4;j<=n;j+=2) ~^~~ main.cpp:199:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(unsigned long long i=3;i<=n;i+=2) ~^~~ main.cpp:202:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(unsigned long long j=i*i;j<=n;j+=i) ~^~~ main.cpp:199:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation] for(unsigned long long i=3;i<=n;i+=2) ^~~ main.cpp:205:9: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for' return s; ^~~~~~ main.cpp: In function 'int main()': main.cpp:256:24: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf(fin,"%d",&n); ^