# C Program for Number of stopping station problem

There are 12 intermediate stations between two places A and B. Find the number of ways in which a train can be made to stop at 4 of these intermediate stations so that no two stopping stations are consecutive?

**Examples –**

Input: n = 12, s = 4Output: 126Input: n = 16, s = 5Output: 792

`#include <stdio.h>` `int` `stopping_station(` `int` `, ` `int` `);` ` ` `// function to calculate number` `// of ways of selecting 'p' non consecutive` `// stations out of 'n' stations` `int` `stopping_station(` `int` `p, ` `int` `n)` `{` ` ` ` ` `int` `num = 1, dem = 1, s = p;` ` ` ` ` `// selecting 's' positions out of 'n-s+1'` ` ` `while` `(p != 1) {` ` ` ` ` `dem *= p;` ` ` `p--;` ` ` `}` ` ` ` ` `int` `t = n - s + 1;` ` ` `while` `(t != (n - 2 * s + 1)) {` ` ` ` ` `num *= t;` ` ` `t--;` ` ` `}` ` ` ` ` `if` `((n - s + 1) >= s)` ` ` `printf` `(` `"%d"` `, num / dem);` ` ` ` ` `else` ` ` ` ` `// if conditions does not satisfy of combinatorics` ` ` `printf` `(` `"not possible"` `);` `}` ` ` `// driver code` `int` `main()` `{` ` ` ` ` `// n is total number of stations` ` ` `// s is no. of stopping stations` ` ` `int` `n, s;` ` ` ` ` `// arguments of function are` ` ` `// number of stopping station` ` ` `// and total number of stations` ` ` `stopping_station(4, 12);` `}` |

**Output:**

126

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