public:

int count[10];

int countDigit(int N, int digit) {

int res = 0;

while(N>1) {

if (N%digit==0) res++;

else break;

N /= digit;

}

return res;

}

bool checkValid(int N) {

int P = 1;

for (int i = 0; i < count[2]; i++) P *= 2;

for (int i = 0; i < count[3]; i++) P *= 3;

for (int i = 0; i < count[5]; i++) P *= 5;

for (int i = 0; i < count[7]; i++) P *= 7;

return P == N;

}

int smallestNumber(int N) {

if (N == 1) return 1;

memset(count, 0, sizeof(count));

count[2] = countDigit(N, 2);

count[3] = countDigit(N, 3);

count[5] = countDigit(N, 5);

count[7] = countDigit(N, 7);

if (!checkValid(N)) return -1;

int res = 0;

res += count[2]/3; count[2] %= 3;

if (count[2] == 2) { res ++; count[2] = 0; }

res += count[3]/2; count[3] %= 2;

res += (count[3] | count[2]);

res += count[5] + count[7];

return res;

}