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#include <vector>#include <cmath>using std::vector;vector<int> list;bool isprime(int nnum);int main() {        int thisnumber;        for(int i = 2; list.size() < 1000000; ++i) {                thisnumber = i;                if(isprime(thisnumber)) {                        list.push_back(thisnumber);                }        }}bool isprime(int nnum) {        int maxfactor = int(sqrt(nnum)), thisfactor;        bool bretval = true;        for(int i = 0; i < list.size(); ++i) {                thisfactor = list[i];                if(thisfactor > maxfactor) {                        break;                }                if(nnum % thisfactor == 0) {                        bretval = false;                        break;                }        }        return bretval;}