>>773
#include<stdio.h>
int main()
{
int n, i;
char m[80];
printf("入力文字列:");
fgets(m, 80, stdin);
printf("キーn = ");
scanf("%d", &n);
for (i = 0; m[i]; i ++) {
if (m[i] >= 'A' && m[i] <= 'Z')
m[i] = (m[i] - 'A' + n) % 26 + 'A';
else if (m[i] >= 'a' && m[i] <= 'z')
m[i] = (m[i] - 'a' + n) % 26 + 'a';
else if (m[i] == '\n')
m[i] = 0;
}
printf("出力文字列:%s\n", m);
return 0;
}