Sieve Of Eratosthenes

#include<cstdio>
#include<cmath>
#include<cstring>

int main() {
     int n;
     n = 2000000; //scanf("%d", &n);
     bool prime[n + 1];
     memset (prime, true, sizeof prime);
     int limit = sqrt ((double) n);
     prime[0] = prime[1] = false;
     for (int i=2; i<=n; i++) {
         if (!prime[i]) continue;
         for (int j=2*i; j<=n; j+=i)
            prime[j] = false;
     }
     for (int i=n; i>1; i--) {
         if (prime[i]) {
             printf("%d\n", i);
             break;
         }
     }
     return 0;
}