Multiply Polynomials

A polynomial of degree n is of the form P(x) = anxn + an-1xn-1 + … + a0. Given two polynomials f(x) and g(x) of degrees n and m respectively, write a program to find the polynomial h(x) given by,
h(x) = f(x) * g(x)

INPUT: Line 1 contains n and m separated by space.
Line 2 contains the coefficients an, an-1…, a0 of f(x) separated by space.
Line 3 contains the coefficients bm, bm-1…, b0 of g(x) separated by space.

OUTPUT: The degree of h(x) followed by the coefficients ck, ck-1…, c0 of h(x) in next line separated by space.

Constraints:
1 <= n <= 10
1 <= ai <= 100

#include<stdio.h>

#include<string.h>

int main()

{

int n,m,i,j,x,a[10],b[10],c[10][10],d[20]={0};

scanf("%d %d",&n,&m);

for(i=n;i>=0;i--)

scanf("%d",&a[i]);

for(i=m;i>=0;i--)

scanf("%d",&b[i]);

for(i=n;i>=0;i--)

{

for(j=m;j>=0;j--)

{

c[i][j]=a[i]*b[j];

}

}

for(x=0;x<=m+n;x++)

{

for(i=0;i<=n;i++)

{

for(j=0;j<=m;j++)

{

if(i+j==x)

{

d[x] += c[i][j];

}

}

}

}

printf("%d\n%d",m+n,d[m+n]);

for(x=m+n-1;x>=0;x--)

{

printf(" %d",d[x]);

}

return 0;

}