diff --git a/problem-204/204.cpp b/problem-204/204.cpp
new file mode 100644
index 0000000..ee4deea
--- /dev/null
+++ b/problem-204/204.cpp
@@ -0,0 +1,73 @@
+#include <cstdio>
+#include <vector>
+#include <cmath>
+
+using namespace std;
+
+typedef unsigned long long int llu;
+
+const llu N = 1000000000;
+const int MAX_PRIME = 100;
+
+int prime_cnt = 1;
+llu primes[ MAX_PRIME ];
+
+void eratosthenes() {
+    primes[ 0 ] = 2;
+
+    for ( llu candidate = 3; candidate < MAX_PRIME; candidate += 2 ) {
+        bool prime = true;
+        for ( int witness = 0;
+              witness < prime_cnt
+           && primes[ witness ] * primes[ witness ] <= candidate;
+              ++witness ) {
+            if ( candidate % primes[ witness ] == 0 ) {
+                prime = false;
+                break;
+            }
+        }
+        if ( prime ) {
+            primes[ prime_cnt++ ] = candidate;
+        }
+    }
+}
+
+inline llu value( vector< llu > factors ) {
+    llu ret = 1;
+
+    for ( int i = 0; i < prime_cnt; ++i ) {
+        ret *= pow( primes[ i ], factors[ i ] );
+    }
+
+    return ret;
+}
+
+inline bool increment( vector< llu > &factors ) {
+    for ( int i = 0; i < prime_cnt; ++i ) {
+        ++factors[ i ];
+        if ( value( factors ) <= N ) {
+            return true;
+        }
+        factors[ i ] = 0;
+    }
+    return false;
+}
+
+int main() {
+    eratosthenes();
+
+    llu total = 0;
+    vector< llu > factorization;
+
+    for ( int i = 0; i < prime_cnt; ++i ) {
+        factorization.push_back( 0 );
+    }
+
+    while ( increment( factorization ) ) {
+        ++total;
+    }
+
+    printf( "%llu\n", total + 1 );
+
+    return 0;
+}
diff --git a/problem-204/eta.cpp b/problem-204/eta.cpp
new file mode 100644
index 0000000..a18f5f4
--- /dev/null
+++ b/problem-204/eta.cpp
@@ -0,0 +1,50 @@
+/*
+ * Simple ETA library for project euler
+ * MIT licensed
+ *
+ * Dionysis "dionyziz" Zindros <dionyziz@gmail.com>
+ */
+#include "eta.h"
+#include <cstdio>
+#include <cassert>
+
+const float EPSILON = 0.0001;
+
+ETA::ETA() {
+    reset();
+}
+
+void ETA::reset() {
+    time( &t1 );
+}
+
+void ETA::get( float completed, int &h, int &m, int &s ) {
+    time_t t2;
+    time( &t2 );
+
+    assert( completed > 0 );
+
+    int diff = ( int )t2 - t1;
+
+    s = ( int )( ( float )diff / completed - diff );
+    // printf( "Total time in seconds: %i\n", s );
+
+    m = s / 60;
+    s %= 60;
+
+    h = m / 60;
+    m %= 60;
+}
+
+void ETA::print( float completed ) {
+    int h, m, s;
+
+    if ( completed < EPSILON ) {
+        printf( "∞" );
+    }
+    else {
+        get( completed, h, m, s );
+        printf( "%d:%02d:%02d", h, m, s );
+    }
+    fflush( stdout );
+}
diff --git a/problem-204/eta.h b/problem-204/eta.h
new file mode 100644
index 0000000..707ecc8
--- /dev/null
+++ b/problem-204/eta.h
@@ -0,0 +1,24 @@
+/*
+ * Simple ETA library for project euler
+ * MIT licensed
+ *
+ * Dionysis "dionyziz" Zindros <dionyziz@gmail.com>
+ */
+#ifndef ETA_H
+#define ETA_H
+
+#include <sys/types.h>
+#include <time.h>
+
+class ETA {
+    public:
+        ETA();
+        void reset();
+        void get( float, int &, int &, int & );
+        void print( float );
+    
+    private:
+        time_t t1;
+};
+
+#endif