watering.c

#include <stdio.h>
#include <stdlib.h>

int wtree( int storey )
{
    return 1 + ( (4 + 2 * ( storey - 1 )) / 2 ) * storey ;
}

int main( int argc, char **argv )
{
    int st;
    if ( argc < 2 ) {
        printf( "Error Input: no argument\n" );
        return 1;
    }

    if ( !( st = atoi( argv[1] ) ) ) {
        printf( "Error: Not entered a number\n" );
        return 2;
    }

    printf( "%d\n",  wtree( st ) );
    return 0;
}