smallest coin

I am trying to find the amount here.
Input

The first line of input contains an integer M, the number of coins in bank.
The second line of input contains M integers: coin1, coin2... coinN. coini represents ith coin.

Output
Print smallest possible amount of cash that you will not be able to pay in super market.

Code:

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int solution(int count_coin, int coin[count_coin])
{
        float coin1=0.50,total=0.0;
        int ncoins;
        printf("Number of 50 coins : ");
        scanf("%d",&ncoins);
        total += (ncoins * coin1);
        printf("** %.2f **",total);
        return;
}

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Also here -> coin smallest - C++ Forum

I am trying to solve this in c programming, maybe the logic that I provided is not working as expected.