int numRows, numCols; scanf("%d %d\n", &numRows, &numCols);

const int primeGap(100);

std::vector<std::vector<long> > numbers(numRows, std::vector<long>(numCols,0));

long currentMax(0);

for(int row = 0; row < numRows; row++){

for(int col = 0; col < numCols; col++){

scanf("%ld", &numbers[row][col]);

if(numbers[row][col] > currentMax){currentMax = numbers[row][col];}

}

}

long upperBound = currentMax + primeGap;

bool * array = new bool[upperBound];

array[0] = array[1] = 0; for(int k = 2; k < upperBound; k++){array[k] = 1;}

for(long k = 0; k < sqrt(upperBound); k++){if(array[k]){for(int m = 2 * k; m < upperBound; m += k){array[m] = 0;}}}

for(int row = 0; row < numRows; row++){

for(int col = 0; col < numCols; col++){

long diff(0);

for(long num = numbers[row][col]; !array[num]; diff++, num++);

numbers[row][col] = diff;

}

}

long minMoves(numRows * numCols * primeGap);

for(int row = 0; row < numRows; row++){

long total(0);

for(int col = 0; col < numCols; col++){total += numbers[row][col];}

if(total < minMoves){minMoves = total;}

}

for(int col = 0; col < numCols; col++){

long total(0);

for(int row = 0; row < numRows; row++){total += numbers[row][col];}

if(total < minMoves){minMoves = total;}

}

printf("%ld\n", minMoves);

return 0;